Method of forming a coating on a surface of a substrate

ABSTRACT

A reinforcing underlayment including dry uniform particles evenly applied to a wet bonding material layer on a surface of a substrate. The substrate, including the layers, is then cured to harden the one or more of the layers. A final coating or topcoat is applied to the cured surface of the substrate. The dry particles are evenly distributed onto the bonding material layer creating a uniform surface for subsequent coatings. The dry particles increase the strength of the liquid coatings increasing solid particle density within the coating system and thereby imparting properties not available for the liquid coatings. The present invention enables a user to easily introduce very heavy, dense, strong particles into a liquid coating and allows the user to apply very dense, heavy particles into and onto a wet bonding material layer followed by a subsequent wet topcoat layer which is cured as one contiguous material with reinforcement and underlayment strengthening coming from the added, dry particles.

PRIORITY CLAIM

This application is a continuation of and claims priority to and thebenefit of U.S. patent application Ser. No. 11/844,708, filed on Aug.24, 2007, which is a continuation of U.S. patent application Ser. No.11/57,001, filed Jun. 20, 2005, now U.S. Pat. No. 7,261,925, which is acontinuation of and claims priority to and the benefit of U.S. patentapplication Ser. No. 10/318,503, filed Dec. 12, 2002, the entirecontents of which are incorporated herein.

CROSS REFERENCE TO RELATED APPLICATIONS

This application relates to the following co-pending commonly ownedpatent application: “ANTI-MICROBIAL ELECTROSURGICAL ELECTRODE AND METHODOF MANUFACTURING SAME,” Ser. No. 11/925,341, Attorney Docket No.3718345-020.

BACKGROUND

Coatings on parts and products are used in industry for severaldifferent purposes. Certain coatings, for instance, are applied tosurfaces to provide low friction, non-stick, abrasion resistant or otherspecific properties. When a harder object contacts a surface andfriction is created, the friction of the force on the surface wears awaya portion of that surface. Over time, the cumulative effect ofrepetitive or continuous contact between the object and the surfacecauses a substantial portion of the surface to wear away so that thesurface is no longer functional. One example of such an object applyingsuch a force is the force applied between metal cooking utensils (i.e.,the objects) and cooking surfaces such as the non-stick coatings appliedto surfaces of pots or pans. Continuous contact between the utensils andthese cooking surfaces causes the coatings applied to the surfaces, suchas non-stick coatings, to gradually wear away and diminish theeffectiveness of the coatings. Therefore, manufacturers have developedabrasion-resistant, non-stick coatings incorporating harder and moredurable particles, which resist the abrasive forces created by cookingutensils as the utensils contact the coated surface of the cookingsurfaces. As a result, these coatings enhance the durability of cookingsurfaces, however, the coatings compromise the non-stick properties ofthe surface. In addition, the introduced hard particles are not attachedfirmly to the surface to provide rigid support of the relatively softnon-stick material topcoat. The loose particles can therefore, dislodgefrom the surface relatively easily.

Wear also occurs, for example, when a surface or surfaces of a componentare subject to continuous and prolonged forces such as rotational orreciprocating forces applied by a first object which basically, rubsagainst the surface of a second object, creating friction between theobjects. The friction generally wears away one or both of the surfaces.If one surface is sacrificial in nature, commonly including softerparticles or materials versus harder particles or materials, it willwear sooner than the surface including the harder, more durable surface.To prevent this, coatings, which are comprised of relatively softmaterials, are applied to a part or parts so that the parts can bereplaced easily when the coating wears out. An example is a PTFE-coatedsolenoid plunger inside a housing of a solenoid which must remain dry orwithout fluid lubrication in use. In operation, the PTFE-coated solenoidplunger wears at a predictable rate due to friction created between thesurface of the plunger and the surface of the housing. Therefore, theplunger can be exchanged for a newly coated plunger on a predictablemaintenance schedule. This is particularly appropriate when no fluidlubricants can be introduced into a system.

Another example of intended sacrificial wear is a wear end plate in arotary gear pump. A thin layer of bronze is attached to, for example, areplaceable iron plate. This plate can be changed when the bronze layerwears.

Other methods of applying reinforcing coatings to surfaces to providewear resistance for soft coatings have been developed. In anotherexample, metal spray coatings, such as bronze, are arc sprayed or flamesprayed onto metal parts to produce an intermittent bronze coating,which is subsequently coated with PTFE and finished into a smoothsurface. The wear resistance of the bronze particles reinforce therelatively weak strength of the PTFE, which has a very low frictionhowever with low wear resistance. This bronze/PTFE coating system willwear longer than a unreinforced PTFE coating.

Coatings are also used for many applications such as for rustresistance, corrosion resistance and as functional or protectivecoatings. In one example, plastic electric motor brush covers are coatedwith coatings containing metal to absorb and conduct electricalemissions to reduce electrical emissions coming from electric fuel pumpsin an automobile or other vehicle.

Coatings may be applied in various different known manners. One methodof applying the coatings is to spray the coatings on to a substrate suchas metallic material. The coatings are usually sprayed so that thecoatings completely cover the surface or surfaces of the substrate thatrequire the coating. Typically, a bonding agent such as primer is usedto initially coat the substrate to promote the adhesion of the coatingto the substrate. The bonding agent or primer is typically applied to acleaned surface of the substrate. Additionally it has been known to addparticles to the liquid primer and/or the base coating to increase theabrasion resistance of the liquid coating and primer. As a result, thecoating or coatings applied to the substrate has greater abrasionresistance.

In one known coating process described in U.S. Pat. No. 5,492,769, hardparticles are embedded in a surface layer on a substrate to improve thescratch or surface wear resistance of the substrate. The surface of thesubstrate is prepared and then a thin layer of discrete, hard particlesare applied to the surface of the substrate. The surface of thesubstrate is then softened using heat or a solvent. The surface may alsobe softened prior to the application of the particles to the surface ifneeded. After the surface of the substrate is softened, the particlesare embedded into the softened surface of the substrate using pressure.The particles are embedded in the surface so that approximately 50% ofthe volume of the particles are located at the surface layer. Thesoftened surface is then allowed to re-harden, which embeds and bondsthe particles to the surface of the substrate. This bonding method isgenerally limited to substrates such as plastics, polymers and softermetals, which are relatively softer than the particles being embedded inthe surfaces of these substrates.

In another known coating process, solid particles are mixed with aliquid primer prior to applying the primer to the surface of thesubstrate. The particles are non-uniform or irregular in shape and theparticles are also non-uniformly dispersed or mixed within the primerbecause the distribution of the particles cannot be controlled.Therefore, as the primer mixture is applied to the surface of thesubstrate, the unevenly distributed particles within the primer tend topool or bunch up on particular areas of the substrate, particularly ifthe particles are very heavy. In addition, heavy introduced particles ina liquid coating system, will settle in different densities onhorizontal, vertical or other pockets or depressions of a coated part.As a result, certain portions of the substrate include more particlesthan other portions of the substrate. This creates an uneven ornon-uniform distribution of introduced particles on the substrate thathas been coated. Thus, when a topcoat or final coat that contains heavyor dense particles is applied to the substrate, the topcoat or finalcoat also pools or builds up in the same areas on the substrate as theparticles in the primer mixture. This diminishes the finish strength orquality of the surface of the finished product.

In a further known coating process, the particles are flame sprayed orapplied in a molten droplet form and propelled onto the surface of thesubstrate. The molten particles adhere to the surface of the substrate.However, the molten particles are typically applied or sprayed onto thesubstrate at such a rate that the molten particles flatten or partiallyflatten as the particles hit or contact the surface of the substrate.Thus, the surface of such substrates are often uneven because of thevarying shapes of the applied molten particles. As described above, thiscauses an uneven surface area or non-uniform surface area so that thecoating that is subsequently applied to the particles is also uneven andnon-uniform.

One known wear resistant coating sold under the trademark Excalibur® byWhitford Worldwide is formed using molten stainless steel particles andprovides non-stick and initial low friction characteristics to surfacesof substrates but is limited in its application exclusively to metalsubstrates. This coating is applied to a substrate surface by first gritblasting the surface with a suitable abrasive to roughen it and promotethe adherence of subsequent material layers. Then, stainless alloyparticles are electric-arc sprayed onto the roughened metal surface ofthe substrate. The particles cool and harden forming varying surfaceconfigurations including high peaks and low peaks, which do notcompletely bond to the surface. Next, several layers of fluropolymercoatings are applied to the particle layer and permanently bond all ofthe coatings in place on the surface of the substrate. The applicationof the molten particles, however, incurs the same problems as describedabove. Thus, the distribution of the size and shape of the moltenparticles in this process are generally not uniform or evenlydistributed on the surface of the substrate.

The varying particle shapes in the above processes and coatings affectthe uniform distribution of the particles on the surface of thesubstrate. The particles are applied to the surface of the substrate toincrease the abrasion resistance of the subsequently applied coating.The irregularly shaped particles generally are not evenly or uniformlydistributed on the surface of the substrate because the irregularsurfaces of the particles generally do not correspond with each other.In addition, particle size may vary where some particles are much largerthan other particles. Thus, some particles bunch together while otherparticles are spread apart based on the size and shape of the particles.This causes the particles to be non-uniformly distributed and be ofnon-uniform size on the surface of the substrate, which in turn, causesthe coating applied to the particles to be non-uniform.

Furthermore, the irregular shape of the particles limits the consistencyof the surface area created by the addition of the non-uniform particlesto the substrate. As described above, irregularly shaped particles maybunch up or be spread apart on a percentage of the surface of thesubstrate and consist of varying heights. Therefore, the maximum surfacearea of each particle may not be exposed to prevent coating weardepending on whether the particles are partially or wholly covered byother particles and whether particles, such as molten metal particles,are deposited on top of previously deposited particles. Because themaximum exposable surface area of each particle is not consistentlyavailable, the total surface area generated by the addition of theparticles to the substrate is limited or diminished. As a result, thebond between the coating and the particles is less consistent and weakerthan if the maximum exposable surface area is exposed for coating bysubsequent topcoats. This results in loose or non-adherent particles ontop of the previously deposited particles.

Another reinforced metal/PTFE coating system consists of an electric arcspray of stainless steel or titanium particles subsequently coated witha two coat PTFE commercial non-stick coating. In one example, analuminum cooking pan is grit blasted with aluminum oxide to roughen thealuminum surface to assist the mechanical attachment of the dissimilarmetal stainless steel or titanium particles to the pan. The stainlesssteel particles are heated to provide molten stainless steel particleswhich are propelled toward the grit blasted surface. The depositedmolten stainless steel or titanium particles cool and the result is arough, varied group of various shaped metal particles which aremechanically attached to the rough grit blasted aluminum surface. Thisirregular surface, which resembles a mountain range of irregular shapedstainless steel particles, is then coated with two or more coatings of acommercial non-stick coating. When cooking utensils contact thereinforced non-stick coating, wear is reduced as the metal particlestake the mechanical abrasion created by cooking utensils.

This stainless steel/PTFE coating system is exemplified by the WhitfordCorporation's Excalibur® coating system. After the stainless particlesare deposited on the aluminum, the Excalibur® coating system includesthe steps of removing non-adherent particles of loose stainless steelfrom the aluminum. The loose, non-adherent or slightly adherentparticles of stainless steel are removed by wire brushing, air cleaningor both prior to the application of the topcoats of PTFE based non-stickcoatings.

Uneven or non-uniform distribution of a coating on a surface of asubstrate causes several different problems or issues for manufacturers.An uneven coating on the surface of a particular part will cause unevenwear of the parts and subject the part to more friction if particlesprotrude through the final coating or topcoat. Conversely, if there areless reinforcing particles in an applied coating due to the non-uniformdistribution of the reinforcing particles in the coating on the surfaceof the part, the coated surface of the part will have less wearresistance or wear protection. Thus, the greater friction and wear onthe part may cause the part to fail during operation or not last as longin operation. Additionally, an uneven coating quality may cause a partto not perform as well in operation. An uneven surface roughness due touneven internally distributed and dispersed reinforcing particles mayalso cause a part or parts requiring specific tolerance levels ordimensions to be outside acceptable limits and therefore not meetdesired designed specifications, fail during assembly or duringoperation. If the coating over the irregular stainless particles isdesigned to provide non-stick or release properties, taller or largerstacked particles protruding through the coating quickly wear, dislodgeeasily and diminish the: desired non-stick or release properties andcause sticking instead of preventing it.

In a mechanical wear situation, if the dispersed lubricant/reinforcingmaterials within the liquid coating, whether the materials are metal ornon-metallic materials, are protruding, mechanical interference may becaused thereby preventing component motion. If the particles are notdispersed uniformly, the wear resistance and consistency of performanceis diminished.

Additionally, liquid coating end use requirements for reinforcing acoating on a surface of a substrate to provide augmentation of, forinstance, a soft coating to increase the wear resistance is presentlyaccomplished by introducing hard particles to the liquid coating. Thedesired laminar placement of specific particles in the coating isimpossible when particles are dispersed in a liquid coating. Theplacement of reinforcing particles within a coating in a specific areais not possible with a liquid coating containing dispersed particles.Furthermore, the placement of different wear resistant particles in aspecific order or location with different properties cannot be done in aliquid coating application. Also, providing an extremely dense, near100% dense layer of reinforcing particles under a smooth topcoat is notpossible with a liquid coating. Even if multiple layers are applied, thepossibility of particles moving and migrating in a liquid coatingprevent assurance of and determination of density before subsequentcoating layers are applied as the liquid carrier reduces the density ofthe interconnected particles. Additionally, if a liquid coatingapplication includes heavy, hard particles such as certain abrasiveparticles, the coating is difficult to apply using conventional pumpsand spray guns, which causes the pumps and spray guns to wear morerapidly.

Accordingly, there is a need for a coating method, and specifically acoating reinforcing underlayment and method of manufacturing same whichenables a reinforced coating system to be evenly, uniformly and denselyapplied to the surface of a substrate.

SUMMARY

The present invention relates in general to coated substrates, andspecifically to a coating reinforcing underlayment for coatingsubstrates on which a topcoat such as PTFE, will be applied and a methodof manufacturing the coating reinforcing underlayment.

One embodiment of the coating reinforcing underlayment of the presentinvention is applied to a substrate, which may be any suitablesubstrate, and which includes a layer of a wet bonding material appliedto the surface of the substrate to be coated and a single layer ofsubstantially uniform dry particles applied directly into and to the wetbonding material layer. In another embodiment, the above process isrepeated until a desired thickness is achieved or until a specificnumber of layers are applied to the surface of the substrate.

In one presently preferred embodiment of the method of the presentinvention, a substrate is positioned on a support so that a surface orsurfaces of the substrate may be coated. Initially, the surface of thesubstrate is cleaned with a cleaner to remove impurities which may bepresent on the surface of the substrate. The cleaner such as a solventmay be manually applied or mechanically applied to the substrate. In oneembodiment, grit blasting or sandblasting is used to clean the surfaceof the substrate. Alternatively, the substrate may be pre-cleaned or themethod may be performed in a “clean room” where the cleaned part ismanufactured and the step is not necessary.

Once the surface of the substrate is cleaned, a layer of a wet bondingmaterial such as a primer is applied to the surface of the substrate.The wet bonding material may include one or more additives which changeor enhance one or more characteristics of the wet bonding material. Forexample, in one embodiment, the wet bonding material includes anultraviolet light cure resin. In another embodiment, the wet bondingmaterial includes an electron beam cure resin. It should also beappreciated that the bonding material may be any suitable bondingmaterial or agent. The bonding material layer is formulated to alsoimprove the bonding capabilities of the subsequent coating layer orlayers applied to the surface of the substrate in addition to retainingthe particles. The layer of wet bonding material is preferably applieduniformly so as to avoid forming a thick layer, which is thicker thanwhat is necessary or required, and avoid drippings which may detractfrom the bonding ability to the substrate.

In one embodiment, while the bonding material layer is still wet, asingle layer of substantially uniform dry particles such as a powderedengineering plastic, dry metal particles, dry ceramic particles orpre-coated or micronized dry particles are sprayed over the wet bondingmaterial. The powdered or dried particles adhere to the wet surface areaof the bonding material in an even manner. In this embodiment, when thewet bonding material is completely coated with one layer of the uniformpowdered particles, additional dry particles cannot stick to the bondingmaterial layer because the adhered particles attached to the bondingmaterial layer act as a barrier to other particles attaching to the wetbonding material layer. Therefore, the dry particles do not build up orform an uneven surface area on the surface of the substrate.Additionally, the wet bonding material layer may be a thick layer wherethe uniform particles sink into and are completely covered by the wetbonding material layer. In another embodiment, the wet bonding materiallayer is a substantially thin layer on the surface of the substrate anda substantial portion of the particles are exposed on the wet bondingmaterial layer. Once applied, the dry particles substantially increasethe surface area of the substrate.

The substantially uniform dry particles are preferably consistent orinclude particles that have substantially consistent granular size andshape. In one embodiment, the particles are substantially round inshape. It should be appreciated that any suitable size or shapedparticles may be employed in the present method such as flat-shaped,flake-shaped, cylindrical-shaped, oblong-shaped or leaf-shaped particlesto suit the end use of the part being coated with this process. In oneembodiment, the dry particle sizes and shapes are determined based onthe end use and desired specifications and chemical composition of thecoated substrate.

In one example, angular particles such as triangular shaped particles orsimilar particles are used to create a rough surface on a substrate byapplying the angular particles to the bonding material layer on thesurface of the substrate. In another example, less abrasive and lowerfriction surfaces are created by using shaped particles such asspherical or round shaped particles. In a further example, one or morecombinations of different shaped uniform particles are used on a surfaceof a substrate. Thus, uniformly sized or shaped groups of uniformparticles or different sized or shaped particles may be applied to asurface of a substrate. The wet bonding material layer and thesubstantially uniform dry particle layer are applied to the surface ofthe substrate until a desired thickness is achieved. Any suitablethickness ranges may be used as desired and determined by themanufacturer. Additionally, the density of the particles may varydepending on the design specifications of an end product or finalproduct. The density or distribution of the particles may vary fromcovering or adhering to approximately ten percent of the surface of thesubstrate to approximately one hundred percent of the surface.Similarly, the density of the uniform particles may vary depending onthe end use criteria.

In another embodiment, low friction uniform particles are applied to alower layer followed by another very thin outer or upper layer of veryfine abrasive particles. This system initially micro-abrades andsmoothes out a counterface or counter surface of relatively rough metalwhich the coating wears against until the abrasive layer is worn down.After the thin abrasive layer is worn, the underlying layer of nonabrasive friction reducing particles provides low friction to the nowsmooth counterface or opposing surface. This embodiment may for instancebe used in shock absorbers where a low quality relatively rough metalinternal surface of tubing is wearing against a coated piston.

The types of coatings and/or uniform particles applied to a substratemay be any suitable type of particle as generally as indicate above. Inone embodiment, whisker or rod shaped particles such as carbon fibers orcarbon whiskers or nickel whiskers are applied to a surface of asubstrate to reduce wear on the surface and provide a non-metallic ormetallic conductive surface for industries where electricallyconductivity is an issue or a requirement. In another embodiment, aramidfibers or engineered plastic particles or fibers are applied to asubstrate to strengthen the surface of the substrate. The aramid fibersinclude Kevlar® or Nomex® fibers which are introduced in substantiallythe same manner as the carbon fibers or whiskers. The Kevlar® or Nomex®fibers or materials can be either a pulp, which includes loose, fluffyfibers which is further ground into fibrillated fine powder, or can beother suitable forms such as round particles or semi-round dryparticles. The aramid particles provide non-metallic wear resistance andhave good bonding ability with both the basecoat and subsequenttopcoats. Thus, the applied aramid fibers or materials create a denselayer of aramid or Kevlar® particles on the surface of the substrate,which is then coated with a topcoat or other suitable final coating.However, if a very high temperature, moderate friction (i.e., lowabrasion) surface is desired, a topcoat or final coating is not appliedto the layer of aramid fibers. In another embodiment, diamond particlesare applied to the wet bonding material layer. Although this option hasa much greater cost than other particles, the diamond particles providegreater wear resistance and less friction on the surface. Theseparticles add tribological benefits beyond those benefits of aramidfibers.

In another embodiment, specially treated, uniform plastic particles areapplied to a surface of a substrate. The plastic particles can bepre-treated PTFE, ultra high molecular weight polyethylene (UHMW) and/orPE or another suitable material are applied to the Wet bonding materialon the surface of the substrate. The particles are irradiated orprocessed with an electron beam which causes changes to the surface ofthe particles, allowing them to wet more easily and to sink into the wetbonding material layer, instead of remaining on the top of the materialbonding layer. Therefore, the plastic particles are strongly bonded tothe layer and not easily dislodged from the surface. This processthereby enables the plastic particle layer to last longer.

In another alternate embodiment, anti-microbial particles such as silveror silver compounds are applied to the surface of a substrate to reduceand kill bacteria and other potential germs that may be located on asurface of a substrate such as a kitchen counter or a food storagevessel, container or a conveyor or hook in a meat packing facility. Inthis embodiment, a dense layer of anti-microbial material in a powder orparticulate form is applied to the wet bonding material layer. In oneaspect of this embodiment, the anti-microbial particle layer is thefinal layer. In another aspect, a thin topcoat or final coating isapplied to the anti-microbial particle layer to provide a release ornon-stick surface on the substrate. The above process can be repeated asnecessary to maintain the effectiveness of the anti-microbial surface.In this aspect, the thin topcoat or topcoats do not completely cover theprotruding anti-microbial particles.

In another embodiment, dry or powdered, ultra porous bronze particlesare applied to the wet bonding material layer on the surface of asubstrate. The ultra porous bronze particles include many openings andvoids so that the particles are approximately seventy percent solidcompared to over ninety percent solid for most porous bronze materials.The particles enable a user to infuse the very porous bronze particleswith the wet bonding material after the bronze particles are depositedon the wet bonding material on a surface of a substrate. This method isused to add lubrication and “lock” or strongly secure the particles intothe liquid bonding material layer to increase the bonding strength ofthe layers to hold the bronze particles to both the upper and lowercoating layers on the surface of the substrate even after being exposedto abrasive forces. The particles may be any suitable porous metalparticles such as stainless steel particles, nickel particles, bronzeparticles, iron particles, titanium particles or other suitableparticles including a metal and/or metal alloys.

In another embodiment, porous metal particles such as the bronzeparticles described above are impregnated or infused with a materialsuch as PTFE, which lowers the friction of the particles. In one aspectof this embodiment, bronze particles or any other suitable metalparticles including approximately seventy percent voids (i.e., air) arevacuum impregnated with a suitable lower friction material such as PTFE.In another aspect of this embodiment, the bronze particles are soakedwith the PTFE and then dried. The latter process leaves partial voids inthe bronze particles. However, the particles are partially infused withPTFE, which adds low friction capabilities to the bronze.

In a further embodiment, catalyzed resins consisting of two parts orplural components such as epoxies or urethanes are used to coat asurface of a substrate. In one example, these catalyzed bonding agentsare used to coat a substrate such as a plastic or low temperature metalto enhance the wear resistance of the surface of the plastic or metalwhile not affecting the strength of the plastic or metal.

In another embodiment, acid or chemical resistance is increased byapplying non-metallic, non-plastic particles such as substantiallyuniform dry ceramic or mica flakes and/or mica particles to the wetbonding material layer. Other suitable particles may be used such asglass, ceramics, modified mica, boron nitride, silicon nitride andaluminum oxide particles. The dry ceramic or mica flakes and/orparticles create a barrier or a substantial barrier to an acid or otherchemical. The barrier created by the particles or flakes diverts theacid or chemical from directly attacking a base material such as ametal, by decreasing the inherent permeability and porosity of a basecoating or coatings on the surface of a substrate. A torturous, indirectpath or maze-like path chemicals must take to reach the underlyingsurface is created by the plates or flakes so that the chemical or acidis forced to take an indirect path around the mica particles or flakesthereby slowing and/or retarding the speed and dynamics of the chemicalor acid that is trying to permeate the coating.

Once the plural component resin followed by dry particles are applied tothe surface of the substrate, the bonding material and substantiallyuniform dry particle layer are cured by catalytic cure, by heating thelayers, air-drying the layers or according to any suitable curingmethod. The curing process cures the resin or dry particles so that astrong bond develops between the substantially uniform dry particlelayer and the wet bonding material layer as it hardens and also bonds;to the base surface. Because the dry uniform particles were applied tothe wet bonding material, the particles are tightly packed and form asingle uniform, substantially even surface on the substrate. As aresult, the substantially uniform dry particles increase the surfacearea on the substrate and enable a topcoat to be applied uniformly andevenly on the substrate. Additionally, the topcoat develops a strongbond with the dry particles below which is bonded to the substrate. Thisprocess may be repeated one or more times to increase the totalthickness and chemical resistance of the coatings on the surface of thesubstrate.

In another embodiment, a wet bonding material layer including relativelysmall particles of a suitable low friction or soft material is firstapplied to the surface of a substrate. Next, a layer of uniform hard dryparticles or other suitable hard particles is applied to the wet bondingmaterial layer. Another layer of the initial wet bonding materialmixture including the relatively smaller particles is then applied tothe dry particle layer. The layers are dried using a suitable drying orcuring process, which causes the top layer or second wet bondingmaterial layer including the small soft particles to shrink anddistribute the small soft particles amongst the hard particles. Thiscreates an abrasion resistant and low friction surface.

The spraying or application of the dry particles to the wet bondingmaterial layer on the surface of the substrate may be adjusted toenhance the strength of the bond between the bonding material and thedry particles and the density of the layers on the substrate. In oneembodiment, the pressure of the dry particle spray and the rate of thespray is increased to increase the density of the particles in thematerial bonding layer. The greater the density of the particles anddepth of the layers, the greater the strength and desiredcharacteristics of the resultant coated substrate.

In another embodiment, an electrostatic, tribo-charged or oppositeelectrostatic charged powder spray method is used to apply the dryparticles to the wet bonding material. The charged particle powder sprayenables an operator to better control the application uniformity of thedry particles and thereby enhance the density and application of the dryparticles to the wet bonding material on the substrate. In a furtherembodiment, the electrostatic powder spray is used to apply a topcoatover the dry particles such as a powder paint coating or fluoronatedplastic powder coating to the surface of the substrate. In thisembodiment, a bonding material and then a conductive material or thinconductivity enhancing coating is applied to the surface of thesubstrate. The powder topcoat or final coating is then cured in aconvection or infrared oven, which heats and shrinks the powder coatingonto the top of the dry particles.

In another embodiment, an applicator such as a sifter is used touniformly apply the uniform particles to the wet bonding material layer.The sifter is similar to a conventional flour sifter and is used incertain applications depending on the size of the uniform particles.

In a further embodiment, ferromagnetic or magnetic dry particles areapplied to a surface of a substrate to completely coat a surface of asubstrate or form a shape, symbol, character or other suitable image ona surface of a substrate. Initially, a non-magnetic metal surface orglass surface or aluminum surface is coated with a wet bonding material.Magnetic particles such as special magnetic stainless steel, magneticferrite or ferrous particles are applied to the wet bonding material.These magnetic particles are attracted to the magnetic shape or symbollying directly under the wet coated glass, aluminum or non-magneticsubstrate, thereby creating a design in the finished coating.

In another embodiment, a surface or a portion of a surface of asubstrate such as the surface of a part is masked or selectively coatedwith a suitable masking device or material so that the dry uniformparticles can only be applied to the unmasked areas on the surface ofthe substrate. In this embodiment, the wet bonding material is generallyapplied to the entire surface or surfaces of the substrate and then amasking material or device is applied to a specific area or areas on thesurface of the substrate. However, the wet bonding material layer can beapplied to a pre-masked substrate to coat the selective areas of thesubstrate. Therefore, the dry uniform particles, which are subsequentlyapplied to the surface of the substrate, adhere to the exposed portionsof the wet bonding material layer but not the masked portions of thesurface of the substrate.

The coating layer applied to the underlayment or wet layer and the drysecond layer may be any suitable coating such as a topcoat layer. Itshould be appreciated that the method of manufacturing or forming thecoating underlayment may be performed as described above by applying orspraying the coatings onto the surface of the substrate. Alternatively,the coatings and dry particles may be applied using other suitablecoating and application methods. In one embodiment, the wet bondingmaterial layer is applied by dipping the substrate either completely orpartially in the wet bonding material layer.

Several different types of additives may be added to the topcoat orfinal coating to improve the performance characteristics of the coatedsubstrate. In one embodiment, a counter face smoothening additiveincluding relatively hard particles, is added to a topcoat or finalcoat, in either a liquid or dry powder form, to enable the coatedsubstrate to smoothen or polish a rough surface or surfaces, whichcontact the surface of the coated substrate. It should be appreciatedthat any suitable additive may be added to the topcoat or final coatingto improve the performance or desired characteristics of the coatedsubstrate.

In another embodiment, the substrate previously coated with a wetbonding material layer and dry particle layer, may be electrostaticallycharged to attract the uniform dry particles having an opposite charge.In this embodiment, substantially uniform dry powder particles areelectrostatically attracted to the substrate because the particles havean opposite charge to the surface of the substrate. In one example, apowder paint coating such as an epoxy or polyester is applied to asurface of a substrate. In this example, a liquid layer is applied to asurface of a substrate and then an electrically conductive dry particlematerial layer is applied to the surface. The powder coating is thenapplied and is electrostatically attracted to the conductive materialouter layer. Because the powder coating does not include solvent, thecoatings are cured in a convection or infrared oven even though thelower layer of the basecoat contains specific solvents. The solvents inthe basecoat migrate through the dry powder before the top powder coatstarts to jell and cure into a continuous coating. The powder coatingheats up and shrinks over the top of the dry particle layer forming auniform, evenly distributed topcoat layer on the surface of the dryparticle layer.

Alternatively, non-electrical, tribo-charged dry paint topcoat particlescan be applied to a grounded part. In this embodiment, a very thin wetlayer remains wet while the powder coat is applied eitherelectrostatically or via a tribo-charge (i.e., friction charge). Theentire coated part is oven cured to simultaneously cure the wet and drypowder topcoats.

In another embodiment, the substantially uniform aluminum oxideparticles are applied to a wet bonding layer surface of a substrate toachieve a desired roughness on the surface. The desired surfaceroughness is achieved by changing the size of the aluminum oxideparticles applied to the surface. The application of the aluminum oxideparticles to roughen a surface substantially minimizes the distortion tothe surface, which occurs with conventional blasting methods, andenables a user to control the roughness of the surface. In addition,harder particles such as boron nitride particles or other suitableparticles can be applied to the surface of the substrate to increase thepenetration resistance of the surface.

In a further alternative embodiment, the dry uniform particles arepre-coated or encapsulated or micro-encapsulated or micronized with abonding enhancing material prior to applying the dry particles to thewet bonding material layer on the surface of the substrate. Thepre-treated particles further enhance the bonding strength of coatedparticles to the layers on the substrate and to subsequent topcoatlayers. The wet bonding material used to pre-coat the dry particles maybe the same or different than the bonding material layer applied to thesubstrate.

In one embodiment, the present method described above is used as acoating to attenuate or reduce magnetic, electromagnetic, radio orsimilar waves generated by electric machines or other devices.Electromagnetic absorbent particles such as metal particles are used tocoat a surface or surfaces. The particles completely coat the surfacesand enhance the electromagnetic, microwave or other wave absorbingcapabilities of the surfaces.

In one embodiment, the present invention may be employed to protectmachine operators from potentially dangerous conditions. Certainmachines such as a Magnetic Resonance Imaging (“MRI”) machines producepotentially harmful conditions. Generally, a MRI machine uses a nuclearmagnetic resonance spectrometer to produce electronic images of specificatoms and molecular structures in solids, especially human cells,tissues, and organs. Exposure to the magnetic frequencies and radiationgenerated by a MRI machine over time may pose health risks to anoperator. Similarly, it is desirable to block exterior magnetic fieldsfrom such equipment. Operators are protected and such equipment isusually protected from exterior magnetic fields by RF enclosures ormagnetically shielded enclosures. Such enclosures include walls oflayers of magnetic shielding material such as copper. Such materialsincluding the fabrication and installation of such materials isrelatively expensive. In accordance with the present invention, denseadsorptive coatings can be applied to the interior and/or exteriorsurfaces of the walls of such enclosures and made of less expensivematerials. The dry particles can be round or flat flakes or combinationsof, for instance, dry copper round and flat particles, assuring completeelectrical conductivity. The dry coating or wet coatings can incorporatesubstances such as metals, which shield and absorb the magneticfrequencies and radiation. If the coatings are applied in a highvibration area, elastomeric urethanes and other suitable flexiblebonding materials may be used to prevent cracking or separations on thecoated substrate.

In another embodiment, a liquid bonding material layer such as an epoxy,which is thermally cured, is applied to the surface of the substrate.Metal particles are then introduced or applied using a dry powder spraymechanism. In one aspect of this embodiment, the metal particles arepassed through a heating chamber or flame device, such as on a metalspray gun. The metal particles pass through an oxyacetylene flameraising the temperature of the particles as the particles are propelledtowards the pre-applied wet bonding layer. Introduction of heat into theparticles allows the wet bonding material layer to start curing orsemi-curing. The curing or semi-curing occurs because the heatintroduced into the coating starts to harden the bonding material layerafter the particles have been immersed in the material layer due to thevelocity and force of the particles propelled at the wet bondingmaterial layer. In a further embodiment, several different metals areapplied to the bonding material. In another embodiment, metals andnon-metals are combined and applied to the bonding material layer toform the underlayment. Additionally, particles formed from a materialfrom the imide family and particles formed from another family such ashigh-end imides can be used to form the reinforcing underlayment.

In an alternative embodiment, a coating system includes a plurality ofcoating applicators, at least one container having a wet bondingmaterial, at least one container having substantially dry particles,wherein the containers are connected to the coating applicators. Thecontainers are connected to the coating applicators with at least onecoating line or tube, which transports the materials from the containersto the coating applicators. It should be appreciated that the coatingapplicators may be spray guns, electrostatic spray guns, powder sprayguns or any other suitable applicators. The coating applicators arepositioned adjacent to the surface or surfaces being coated on thesubstrate. Additionally, the coating applicators may apply the coatingsat the same rate or at different rates.

In one example, multiple coating applicators such as two electrostaticspray guns or powder spray guns, apply an epoxy-based material to asurface of a substrate. The epoxy is made up of relatively dry particleswhich are applied using electrostatic attraction to the surface. Whilethe epoxy is in place, a thin layer of a wet bonding material isfog-sprayed or applied to the epoxy particles to slightly dampen thesurface of the particles. Then, a powder spray of aluminum oxide,bronze, ceramic, glass or any other suitable material is applied to thebonding material on the particles. The layers are then heated or curedat one time. Subsequently, a final coating such as a wet or dry coatingmay be applied to the cured layers as a final coating or topcoat.

In another embodiment, one or more additional bonding material layersare applied to the first or primary bonding material layer applied tothe surface of the substrate to meet specific design specifications orcoating requirements of a manufacturer. The bonding material layers maybe the same or different bonding materials and are applied to the firstbonding material layer until a predetermined thickness is achieved. Theuniform dry particles may be applied to any one of the reinforcingmaterial layers on the surface of the substrate. Additionally, differentmaterials may be added to the bonding material layer or layers, based onspecific design specifications.

In a further embodiment, the coated substrate is cured using inductionheating. In this embodiment, induction sensitive particles such as metalparticles are applied to the wet bonding material on the surface of asubstrate. The metal particles are rearranged in the wet bondingmaterial using a magnet and induction waves, which are reverse magneticfields, are then directed at the coated substrate to induce heat in thewet bonding material. The heat induced in the wet bonding material curesthe wet bonding material. In another embodiment, an induction heatdevice is used to raise the temperature of the substrate and therebycures the wet bonding material layer.

It is therefore an advantage of the present invention to provide areinforcing underlayment and a method for manufacturing the reinforcingunderlayment that increases the desired final system characteristics ofa substrate.

Another advantage of the present invention to provide a reinforcingunderlayment and a method for manufacturing the reinforcing underlaymentthat enhances, improves or changes the inherent characteristics of asubstrate or surface.

A further advantage of the present invention is to provide a method formanufacturing for a coating underlayment which enables the underlaymentto be applied to a substrate as a single, even and substantially uniformlayer of particles.

Another advantage of the present invention is to provide a method ofmanufacturing a coating underlayment that employs substantially uniformparticles to form the underlayment layer on a substrate.

A further advantage of the present invention is to provide a method ofmanufacturing a coating underlayment that employs different sizedparticles and particles of different chemistries and characteristics toform the underlayment layer on a substrate.

Another advantage of the present invention is to provide a coatingunderlayment and method of making the coating underlayment that can beused on a wide variety of temperature sensitive substrates and products.

A further advantage of the present invention is to provide a coatingunderlayment apparatus and method which significantly reduces capitalequipment costs, operation costs and process complications.

Additional features and advantages of the present invention aredescribed in and will be apparent from, the following DetailedDescription of the Invention and the Figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is an enlarged fragmentary side view of a coated substrate ofone embodiment of the present invention.

FIG. 1B is an enlarged fragmentary cross-sectional view of the coatedsubstrate of FIG. 1A taken substantially along the line 1B-1B.

FIG. 1C is an enlarged fragmentary side view of a coated substrate ofanother embodiment of the present invention including angular particlesdistributed on the surface of the substrate with different densities.

FIG. 1D is a top view of the embodiment of FIG. 1C.

FIG. 1E is an enlarged fragmentary side view of a coated substrate ofanother embodiment of the present invention including sphericalparticles distributed on the surface of the substrate with differentdensities.

FIG. 1F is an enlarged fragmentary side view of a coated substrate ofanother embodiment of the present invention including flake-shapedparticles distributed on the surface of the substrate with differentdensities.

FIG. 1G is an enlarged fragmentary side view of a coated substrate ofanother embodiment of the present invention including fiber particlesdistributed on the surface of the substrate with different densities.

FIG. 1H is an enlarged fragmentary side view of a coated substrate ofanother embodiment of the present invention including spherical andflake-shaped particles distributed on the surface of the substrate withdifferent densities.

FIG. 1I is an enlarged fragmentary side view of a coated substrate ofanother embodiment of the present invention including spherical andfiber particles distributed on the surface of the substrate withdifferent densities.

FIG. 1J is an enlarged fragmentary side view of a coated substrate ofanother embodiment of the present invention including fiber andflake-shaped particles distributed on the surface of the substrate withdifferent densities.

FIG. 2A is an enlarged fragmentary side view of a coated substrate of aanother embodiment of the present invention illustrating angularparticles applied to the bonding material layer on the surface of asubstrate.

FIG. 2B is an enlarged fragmentary side view of the embodiment of FIG.2A where an abrasion resistant coating is applied to the angularparticle layer on the surface of the substrate.

FIG. 3A is an enlarged fragmentary side view of a coated substrate of aanother embodiment of the present invention illustrating different sizedparticles applied to the bonding material layer on the surface of asubstrate.

FIG. 3B is a top view of the embodiment of FIG. 3A.

FIG. 3C is an enlarged fragmentary side view of a coated substrate of afurther embodiment of the present invention illustrating different sizedparticles applied to the bonding material layer on the surface of asubstrate.

FIG. 3D is a top view of the embodiment of FIG. 3C.

FIG. 4 is a flowchart illustrating one embodiment of the coating methodof the present invention.

FIG. 5A is an enlarged fragmentary side view of a coated substrate of afurther embodiment of the present invention illustrating flake-shapedparticles applied to the bonding material layer on the surface of asubstrate.

FIG. 5B is an enlarged fragmentary side view of a coated substrate ofanother embodiment of the present invention illustrating the wearpattern of ultra porous particles applied to the bonding material layeron the surface of a substrate and the attachment of the 80% wornparticles due to the anchor pattern of attachment or bonding siteswithin the porous particles.

FIG. 5C is an enlarged fragmentary side view of a coated substrate of afurther embodiment of the present invention illustrating ultra porousmetal particles infused with smaller particles and a topcoat containingwear and friction reducing agents.

FIG. 5D is an enlarged side view of one of the infused ultra porousmetal particles of the embodiment of FIG. 5C.

FIG. 6A is an enlarged fragmentary side view of a coated substrate ofanother embodiment of the present invention illustrating a coatedsubstrate including a coating layer applied to the bonding materiallayer.

FIG. 6B is an enlarged fragmentary cross-sectional view of the coatedsubstrate of FIG. 6A taken substantially along the line 6B-6B.

FIG. 6C is a top view of the embodiment of FIG. 6A.

FIG. 7A is an enlarged fragmentary side view of a coated substrate of afurther embodiment of the present invention illustrating a coatedsubstrate including multiple underlayment layers and dry particles ineach individual layer.

FIG. 7B is an enlarged fragmentary cross-sectional view of the coatedsubstrate of FIG. 7A taken substantially along the line 7B-7B.

FIG. 7C is an enlarged fragmentary side view of a coated substrate ofanother embodiment of the present invention illustrating a coatedsubstrate including multiple underlayment layers having sphericalparticles introduced into each individual layer.

FIG. 7D is an enlarged fragmentary cross-sectional view of the coatedsubstrate of FIG. 7C taken substantially along the line 7D-7D.

FIG. 7E is an enlarged fragmentary side view of a coated substrate ofanother embodiment of the present invention illustrating a coatedsubstrate including multiple underlayment layers having angularparticles.

FIG. 7F is an enlarged fragmentary cross-sectional view of the coatedsubstrate of FIG. 7E taken substantially along the line 7F-7F.

FIG. 8 is an enlarged fragmentary side view of a coated substrate of afurther embodiment of the present invention illustrating the uniformparticles as substantially uniform round particles.

FIG. 9 is an enlarged fragmentary view of a coated substrate of anotherembodiment of the present invention illustrating multiple wet materialbonding layers including hard and soft particles applied to the surfaceof the substrate.

FIG. 10A is an enlarged fragmentary view of an example of the coatedsubstrate of FIG. 9 illustrating a stage of the process for forming thecoating on the substrate.

FIG. 10B is an enlarged fragmentary view of an example of the coatedsubstrate of FIG. 9 illustrating the final stage of the process forforming the complete coated substrate.

DETAILED DESCRIPTION Reinforcing Underlayment

Referring now to FIGS. 1A and 1B, one embodiment of a product includingthe coating reinforcing underlayment of the present invention isillustrated where a coating such as a topcoat material is applied to anunderlayment. In this embodiment, a reinforcing underlayment 103 aincludes a wet bonding material layer 104 a and a single layer ofsubstantially uniform dry particles 106 a which are appliedsubstantially evenly to the bonding material layer on a surface of thesubstrate or product as shown in FIG. 1A. The reinforcing underlaymentof the present invention is employed or used to facilitate the adherenceof a coating to at least a portion of the surface of the substrate. Thesubstrate 102 a generally may be any suitable type of substrate such asa metal, wood, plastic, glass or other suitable material.

A layer of wet bonding material 104 a such as a separate layer of anadhesion promoter or other suitable material or mixture of materials, isapplied to the surface of the substrate to be coated to promote theadhesion of subsequent layers to the substrate. In one embodiment, thewet bonding material is a ultraviolet light cure resin. In anotherembodiment, the wet bonding material includes an electron beam cureresin. It should be appreciated that the bonding material layer 104 amay be any suitable wet bonding material with or without one or moreadditives which change or enhance one or more characteristics of the wetbonding material. In one embodiment, the wet bonding material layer orfilm thickness ranges from five microns to one hundred fifty microns orlarger. The wet bonding material layer may therefore be a thick layerwhere the uniform particles sink into and are completely covered by thewet bonding material layer. In another embodiment, the wet bondingmaterial layer is a substantially thin layer on the surface of thesubstrate and only a small portion of the particles adhere to the thin,wet bonding material layer. Furthermore, the reinforcing underlayment103 a includes a single layer of substantially uniform dry particles 106a, which are evenly distributed or applied to the wet bonding materiallayer 104 a. After the dry particles 106 a are applied to the wetbonding material layer and the wet bonding layer is cured, a reinforcingmaterial topcoat layer or reinforcing topcoat coating 108 a is appliedto the reinforcing underlayment 103 a. The reinforcing topcoat coating108 a may be any suitable type of material or coating applied tosubstrates such as a topcoat, paint, a corrosion protective coating orother suitable materials or coatings that can be mixtures of solidparticles and liquid materials. It should also be appreciated that thereinforcing topcoat coating may be any suitable topcoat such asultraviolet light cure resins or electron beam cure resins. One or morereinforcing material layers or reinforcing coatings may be applied tothe layer of dry particles based on the design specifications and thedesires of the manufacturer. The reinforcing material layers or coatingsmay be the same materials or coatings, or different materials orcoatings. In one embodiment, the final topcoat reinforcing materiallayer(s) is/are applied to the dry particle layer until a predeterminedor desired thickness is achieved. In another embodiment, the reinforcingmaterial layers and/or coatings are applied until the layers and thesubstrate are a predetermined or desired total or overall thickness.

After the coatings have been applied to the substrate, the resultantstructure of the underlayment 103 a includes the dry particles orgranules introduced into the wet bonding material layer where the wetbonding material layer adheres to various types of surfaces of asubstrate such as round or flat surfaces. In a curing process, the dryparticles 106 a remain in place completely covering the wet bondinglayer 104 a while the wet bonding material layer 104 a passes throughphases until the dry particles and the bonding material layer are fusedtogether as the liquid layer is cured. It should be appreciated that thebonding material layer 104 a and uniform dry particles 106 a may bepartially cured or completely cured depending on whether single ormultiple bonding material and dry particle layers are applied to thesurface of the substrate.

Referring to FIGS. 1C and 1D, another embodiment of the presentinvention is illustrated where the coated substrate includes uniformsize angular particles distributed with varying densities on the surfaceof the substrate. This type of distribution may be employed on productssuch as cooking equipment where greater abrasion resistance is desiredin specific areas. For example, the denser distribution of particles isapplied to the more abrasive areas to minimize the effects of theabrasion on the surface. In FIG. 1C, a bonding material layer 104 b isapplied to the surface of the substrate 102 b. The angular particles 106b are then applied with different distributions or varied densities onthe surface. The particles are applied to a suitable thickness such asthe thickness 103 b. A topcoat or final coating 108 b is applied ifdesired, such as PTFE. In one embodiment, the topcoat is a suitablesolvent which is applied over the particles after the particles areapplied to the wet bonding material. The capillary action of thesolvents draws some of the wet bonding material up over the particles asthe solvent evaporates to strengthen the bond of the particles to thewet material bonding layer. The final coated substrate 100 b thereforeincludes different densities of uniform particles as shown in FIG. 1D.

Referring to FIGS. 1E to 1J, different types of particles and differentcombinations of particles may be applied to the wet bonding materiallayer on the surface of the substrate. In FIG. 1E, different densitiesof spherical particles 106 c are applied to the wet bonding materiallayer. In FIG. 1F, different densities of flake-shaped particles 106 dare applied to the wet bonding material layer. In FIG. 1G, differentdensities of fiber particles 106 e are applied to the wet bondingmaterial layer. In FIG. 1H, different densities of a combination ofspherical particles 106 c and flake-shaped particles 106 d are appliedto the wet bonding material layer. In FIG. 11, different densities of acombination of spherical particles 106 c and fiber particles 106 e areapplied to the wet bonding material layer. In FIG. 1J, differentdensities of a combination of flake-shaped particles 106 d and fiberparticles 106 e are applied to the wet bonding material layer. It shouldbe appreciated that any suitable combinations of the above particles maybe applied to the wet bonding material layer depending on the end-userequirements and specifications.

The coating underlayment is primarily composed of substantially uniformdry particles, which form a single substantially uniform andsubstantially even layer on the surface of the substrate or product. Inone embodiment where abrasive resistant surfaces are desired, thesubstantially uniform dry particles may be any suitable size or shape asdesired by the manufacturer such as flat-shaped, flake-shaped,angular-shaped, cylindrical-shaped, oblong-shaped and leaf-shapedparticles. Specifically, the substantially uniform dry particles aresubstantially the same in size and shape for several reasons, includingso that the coating area or area of adhesion is maximized on the surfaceof the substrate. In one embodiment shown in FIG. 2A, angular particles206 such as triangular shaped particles are used to create a roughsurface on a substrate by applying the angular particles to the bondingmaterial layer 204 on the surface of the substrate 202. In anotherembodiment, softer, less abrasive surfaces are created by using shapedparticles such as spherical shaped particles. In a further exampledescribed in more detail below, combinations of different shapedparticles are used on a surface of a substrate as shown in FIGS. 3A and3B. Thus, uniformly sized or shaped particles or different sized orshaped particles may be applied to a surface of a substrate.

As indicated above, in one preferred embodiment, the wet bondingmaterial layer and the substantially uniform dry particle layer areapplied to the surface of the substrate until a desired thickness isachieved. In one presently preferred embodiment, the desired thicknessis approximately 5 μm to 100 μm. Other suitable thickness ranges may beused as desired by the manufacturer. In FIG. 2B, an abrasion resistanttopcoat or final coating 208 is applied to the angular particles 206.The abrasion resistant coating further enhances the abrasion resistantcharacteristics of the surface of the substrate.

In another embodiment, the substantially uniform dry particle layer iscomposed of substantially spherical particles, which creates a softer,less abrasive surface on the substrate. It should be appreciated thatthe particles may be spherical particles, substantially flat flakes,fibers or any suitable shape or combination of shapes as describedabove, which maximizes the surface area of the uniform particle layer.Additionally, the size of the dry particles may be changed as desired toaccommodate different technical and coating requirements orspecifications. In one embodiment, the dry particles include at leastone relatively large particle and at least one relatively smallparticle. In another embodiment, the dry particles range in size such asfrom a sub-micron to approximately 125-150 microns.

The density of the uniform particles on the wet bonding material layeron the surface of a substrate may be changed or enhanced to strengthenthe bond of the particles in the layer. In one embodiment, the particlesare applied to the wet bonding material layer and then the part isvibrated to settle the particles into the wet bonding material layer. Inanother embodiment, a wet bonding material layer and a layer ofsubstantially uniform particles are applied to a surface of a substratesuch as a round part having an internal bore. The part is rotated, whichcauses the particles to densify or pack together in the wet bondingmaterial due to the centrifugal force of the spinning part.

Referring to FIGS. 3A and 3B, the uniform particle layer includesdifferent sized spherical particles 306 a and 306 b applied to thebonding material layer 304 on the surface of the substrate 302. In oneexample, the smaller sized particles 306 b are softer particles and thelarger sized particles 306 a are harder particles such that the softparticles provide lower friction and the hard particles enhance theabrasion resistance of the surface as described in more detail below.Another example, hard abrasion resistant larger size particles andsmaller electrically conductive particles are applied to create anabrasion resistant and electrically conductive reinforcement underlayer.A topcoat or final coating 308 of a suitable material is applied to theuniform particle layer. In FIGS. 3C and 3D, another aspect of thisembodiment is illustrated where different sized angular particles 306 cand 306 d are applied to the wet bonding material layer 304 on thesurface of the substrate 302. It should be appreciated that any sizesand shaped particles may be applied to the surface of the substrate.

Coating Underlayment Method

Referring to FIG. 4, one embodiment of the method of applying thecoating underlayment to form a coated substrate is illustrated in theflow diagram. In the method illustrated in FIG. 4, one or more surfacesto be coated on a substrate are cleaned using a suitable cleaner asindicated in block 400. The cleaner removes a substantial portion of orall of the impurities that may be on the surface of the substrate whichmay inhibit the adhesion of one or more of the layers to the substrate.The surfaces to be coated may be cleaned manually or mechanically in anautomated process. The substrate may be cleaned using any suitablecleaning process such as grit blasting or sandblasting, which slightlyroughens and cleans the surface or surfaces of a substrate.Additionally, the substrate may be pre-cleaned in a clean room orsimilar manufacturing area where the step described in block 400 is notnecessary.

After the substrate is cleaned or is clean, a layer of a substantiallywet bonding material is applied to the substrate as indicated by block402. The bonding material provides a wet or moist surface for thesubsequent substantially uniform dry particle layer to adhere to. Thewet bonding material may be any suitable bonding material, which meetsthe specific design specifications of the particular product orsubstrate. In this embodiment, it is important that the bonding materialremain wet prior to the application of the uniform dry particle layer sothat the dry particles stick to or adhere to the wet bonding material.As described in block 404, in this embodiment, a single layer ofsubstantially uniform dry particles are applied or sprayed onto the wetbonding material layer until the wet bonding material layer iscompletely coated with the dry uniform particles and a desired thicknessis achieved. The thickness of the coatings or coating layers isdependent on the specifications for the particular product, the amountof bonding material applied and the size and shape of the dry particles.

In one embodiment, the substantially uniform dry particles are sprayedor applied onto the wet bonding material as a single substantiallyuniform and substantially even layer which adheres to the sticky or wetsurface of the bonding material. In another embodiment, the substrate iselectrically grounded using a suitable grounding method. Grounding thesubstrate thereby grounds the wet bonding material layer, which isformulated to include solvents and/or liquids that conduct electricalenergy. The substantially uniform dry particle layer has or will have anopposite electrical charge to that of the bonding material layer andtherefore is electrically or electrostatically attracted to the wetbonding material layer as the dry particles are applied to that layer.In a further embodiment, an applicator such as a sifter is used touniformly apply the uniform particles to the wet bonding material layer.The sifter is similar to a conventional flour sifter or a drum sifterand is used in certain applications depending on the requiredapplication of the uniform particles.

In another embodiment illustrated in FIG. 5A, an electrically conductiveliquid bonding material layer is applied to the surface of the substrateto enhance the attraction of the dry particles, which may be materialflakes (as shown in FIG. 5), ceramic or plastic particles and alsospecially treated or untreated particles, such as bronze, brass, zinc,copper, steel, stainless steel, aluminum, graphite, titanium, molybdenumdisulfide, molybdenum, talc, lead, antimony, tin, silver, titanium andnickel or any other suitable metals, alloys, ceramics or plastics. Theoppositely charged or tribo-charged (i.e., friction charged) electricalattraction of the dry particles or flakes 506 to the wet bondingmaterial layer 504 promotes the adhesion and uniformity of coverage ofthe dry particles to the bonding material layer. The metal particles canbe propelled toward the wet surface with air or gasses that have beenionized or treated to momentarily electrically charge the metalconductive particles with the opposite charge of the wet surface of thesubstrate. The result is a dense, substantially uniform and evenlydistributed particle layer or underlayment layer on the surface of thesubstrate 502.

In another embodiment, a liquid bonding material layer such as an epoxy,which is thermally cured, is applied to the surface of the substrate.The metal particles are then introduced using a dry powder spraymechanism. In one aspect of this embodiment, the metal particles arepassed through a heating chamber or flame device, such as on a metalspray gun. The metal particles pass through an oxyacetylene flameraising the temperature of the particles as the particles are propelledtowards the pre-applied wet bonding layer. Introduction of heat into theparticles allows the wet bonding material layer to start curing orsemi-curing. The curing or semi-curing occurs because the heatintroduced into the coating starts to harden the bonding material layerafter the particles have been immersed in the material layer due to thevelocity and force of the particles propelled at the wet bondingmaterial layer.

In a further embodiment, several different metals are applied to abonding material layer on a surface of a substrate. In one example,bronze particles having a size of 35-microns and lead particles having asize of 5-microns are sequentially applied to a bonding material layeron a surface of a substrate. In another example, metals and non-metalsare combined to form the underlayment. For instance, bronze particlesand pre-cured imide-amide particles can be applied to the bondingmaterial layer. Additionally, particles formed from a material from theimide family and particles formed from another family such as high-endimides can be applied to the bonding material layer. This combinationallows the bronze to dissipate or absorb surface heat and conduct heataway from the surface of the substrate. The engineering plasticmaterials described above can be used instead of the bronze particles ifmuch lower friction is desired.

Referring now again to FIG. 4, after the substantially uniform particlelayer is applied to the bonding material layer, the layers are cured tostrengthen the bond between the uniform dry particle layer and the wetprimer layer on the surface of substrate as indicated by block 406. Thecuring process may be performed by heating the layers at a predeterminedtemperature or temperatures, air-drying the layers or by utilizing anysuitable internal or external curing or cross linking process. Inaddition, the curing process may use a single or plural package heatcure or air-dry materials, such as polyimide for heat cure applicationsand acrylics for air-dry applications and two part epoxies for roomtemperature or U.V. rapid curing. When the substantially uniform dryparticle layer has completed adhered or bonded to the bonding materiallayer, a suitable coating layer is applied to the uniform dry particlelayer as indicated in block 408. The coating may be any suitable coatingsuch as a topcoat or final coat material. Examples include corrosive orabrasive resistant coatings, non-stick coatings or low friction coatingsand electrically insulative or conductive coatings or combinationsthereof.

The substantially uniform dry particle layer maximizes the surface areaexposed to the coating applied to that surface of the particles.Increasing the surface area for the application of a coating to thatarea, enables the coating to develop a very strong mechanical bond tothe underlayment layer and ultimately to the substrate. The strong bondbetween the coating and the underlayment layer promotes the durabilityand strength of the coating on a product or substrate. Furthermore, thecoating underlayment layer also promotes a substantially even anduniform distribution of the coating to the substrate. Optimum adhesionis provided by the first wet bonding layer on the surface to thesubsequently applied particles. The second wet coating is formulated toprovide optimum adhesion to the particles and provide specificcharacteristic to the final surface as determined by the use of thefinal surface. This minimizes the defects or uneven distribution of thecoating on the surface of the substrate and promotes the maximumfunctional values of the coated part. Thus, less parts or products arediscarded due to uneven coating or defective coating layers on asubstrate or product and the coating provides the maximum functionalcharacteristics with minimal compromises of the functionalcharacteristics of the finished or complete coating.

Uniform Particle Embodiments

The types of particles applied to the surface of a substrate vary basedon the specific requirements of a substrate or based on the environmentin which the substrate is being used. In one embodiment, dry or powderedcarbon particles or whiskers such as carbon fiber particles or whiskersare applied to a substrate to prevent wear of a surface on the substrateand to provide a non-metallic conductive surface. The dry or powderedcarbon fibers are substantially uniform fibers applied to a wet bondingmaterial layer such as a primer on a surface of a substrate. In oneexample, a substrate including carbon fiber particles is used for hightemperature commercial knives and cutting blades where staticelectricity must be dissipated. In another example, a substrateincluding carbon fiber particles is used for conveyors to transportpaper and other static electricity producing materials, such as plastic.In this embodiment, the wear reduction capabilities of a substrate arevastly improved with the carbon fibers, which can be as small asapproximately three microns in diameter and approximately 20-30 micronslong. When the carbon fibers are dry sprayed onto the bonding materiallayer, the shorter fibers orient themselves in multiple directionsthereby enhancing the wear resistance of the carbon fiber layer (the endof the carbon fiber particles do protrude through the final coatingsurface). The bonding matrix is designed according to end use or designspecifications. The carbon fibers may include a high or low temperaturematerial.

In another embodiment, aramid fibers or engineered plastic particles orfibers are applied to a substrate to strengthen the surface of thesubstrate. The aramid fibers may any suitable aramid material such asKevlar®, which is manufactured and sold by the E.I. du Pont de NemoursCompany. The aramid or Kevlar® fibers are applied to the bondingmaterial layer in very much the same manner as the carbon fibers orwhiskers. The Kevlar® fibers or materials can be either a pulp, whichincludes loose, fluffy fibers which is further ground into a finepowder, or can be other suitable forms such as round particles orsemi-round particles. The aramid particles provide non-metallic wearresistance and have good bonding ability with both the basecoat andsubsequent topcoats. Thus, the applied aramid fibers or materials createa dense layer of aramid or Kevlar® particles on the surface of thesubstrate, which is then coated with a topcoat or other suitable finalcoating. However, if a very high temperature non-metallic ornon-ceramic, moderate friction (i.e., low abrasion) surface is desired,a topcoat or final coating is not applied to the layer of aramid fibersas in a brake surface or clutch facing, or a specific high temperaturetopcoat formulation may be applied as an option.

In another embodiment, individual and/or combinations of aramid fibersor particles, which may be any random shape and size, are applied to thesurface of the substrate. In this embodiment, the dry aramid particlesor fibers are applied to the wet bonding layer, which has beenpreviously applied to the surface of the substrate. Because the aramidfibers have extreme temperature resistance compared to most polymers andorganics, the aramid fibers or particles can be topcoated with a veryhigh temperature PTFE or silicone type resin. Therefore, the temperatureresistance, non-stick capability and wear resistance of the final coatedsurface is equivalent to and sometimes greater than the same propertiesfor metal fibers or particles.

In one example, the aramid fibers are used as a clutch facing or in abraking mechanism in a tightly contained space. In this example, analuminum brake shoe is pre-coated with a wet silicone or hightemperature imide-amide material layer, then a layer of aramid fibers orparticles, followed by another wet silicone or imide-amide layer, andthen a imide-amide particle material layer. In one example applicationof the present invention, a motorcycle clutch disc is manufactured ofaluminum and then, using this method to provide wear resistance,eliminates the steel clutch disc construction and reduce the weight ofthe clutch assembly by more than fifty percent. The aramid fibers reduceand prevent galling and seizure of counter surfaces because of thearamid fibers extremely high temperature capability and ability to charand ablate at the outer surfaces in the presence of oxygen and highscuffing at relative speeds. Additionally, a thin topcoat of PTFE,graphite or another suitable lubricant film can be applied to the aramidparticle layer to assist the break in of the counter surface orsurfaces.

In a further embodiment, specially treated, uniform plastic particlesare applied to a wet bonding layer as applied to a substrate. Theplastic particles are pre-treated PTFE, UHMW and/or polyethylene (PE) oranother suitable material and applied to the wet bonding material on thesurface of the substrate. The particles are pre-irradiated or processedwith an electron beam or other suitable method which causes theparticles to be able to sink into the wet bonding material layer,instead of remaining on the top of the wet material bonding layer.Therefore, the plastic particles are strongly bonded to the layer andnot easily dislodged from the surface. This process thereby enables theplastic particle layer to last longer.

In another embodiment, dry or powdered anti-microbial particles whichreduce and kill bacteria and other microbials are applied to the wetbonding material layer on the surface of a substrate. In one aspect ofthis embodiment, a final coating or topcoat is not applied to the dryanti-microbial particles or powder layer, which enables theanti-microbial particles to remain at the surface. In another aspect ofthis embodiment, a thin topcoat or final coating such aspolytetrafluorethylene (PTFE) is applied to the anti-microbialparticulate layer to perform a release function such as a non-stickcoating on the surfaces of cooking equipment. In one example, a countertop such as a kitchen counter, is coated with a two part epoxy followedby a powder coating of anti-microbial material. Then, a thin coating ofthe epoxy is applied to the anti-microbial particulate layer as a finalcoating or topcoat. Such a counter may be used in a meat packing plantto kill harmful bacteria on counters where the meat is cut and packagedor the anti-microbial coating may be used on hooks or similar conveyingequipment in a meat packing house. The anti-microbial effect of thecoatings on the counters can be maintained by repeating the coatingprocess on the counter surfaces periodically as needed. It should beappreciated that any suitable anti-microbial particles or material suchas silver, silver-ceramic or silver compounds may be used in the aboveembodiment.

In a further embodiment, dry or powdered, ultra porous bronze or otherporous particles are applied to the wet bonding material layer on thesurface of a substrate. The ultra porous bronze particles are“sponge-like” particles that include many openings and voids such thatthe particles are approximately seventy percent solid compared to overninety percent solid for other porous bronze materials. The ultra porousbronze particles are infused with the wet bonding material after thebronze particles are deposited on the wet bonding material on a surfaceof a substrate. The infused or vacuum infused material layer permeatesthe pores of the bronze particles and bonds to the “mini-tunnels” in theparticles. The infused layer adds lubrication and increases the bondingstrength of the layers to hold the bronze particles to both the upperand lower coating layers and to the surface of the substrate. Thus, thisprocess “locks” the ultra porous particles into the wet bonding materiallayer, which prevents the particles from dislodging easily from the wetbonding material layer as they wear.

FIG. 5B illustrates the secure bond of the ultra porous particles in thebonding material layer. The ultra porous particles are applied to a wetbonding material layer 510 on the surface of a substrate 508 asdescribed above. In addition, a topcoat or final coating 513 of asuitable material such as PTFE is applied to provide further wearresistance. In FIG. 5B, Section I shows that initially one hundredpercent of the ultra porous particles are applied to the wet bondingmaterial where there is zero percent wear of the particles. After thetopcoat 513 is completely worn away and after the ultra porous particlesare worn down to approximately fifty percent of the particles originalsize as shown in Section II of FIG. 5B, the particles still stronglyadhere to wet bonding material 510. As shown in Section III, after someadditional time, almost all of the particles remain adhered to thebonding material layer even after approximately eighty percent of theparticles has been worn away. In one embodiment, a special topcoat layerincluding a high solid material which migrates into the pores of theattached bronze particles is applied to the particles, either after thefirst curing process or as part of the first bonding material layerapplied to the surface of the substrate.

In another embodiment, porous metal particles such as the bronzeparticles described above are impregnated or infused with a materialsuch as PTFE, which lowers the friction of the particles. In one aspectof this embodiment, bronze particles defining or including seventypercent voids (i.e., air) is vacuum impregnated with a suitable materialsuch as PTFE. In another aspect of this embodiment, the bronze particlesare soaked with the PTFE and the dried. The latter process leavespartial voids in the particles where the particles are approximatelyforty percent solids. It should be appreciated that any suitable metalor metal alloy or ceramic particle or particles may be used as the baseparticles. It should also be appreciated that any suitable low frictionmaterial such as PTFE, anerobic polyester and UHMW may be used to fillor partially fill the voids.

Referring to FIGS. 5C and 5D, in another embodiment, a topcoat material526 including lubricative particles 527 is applied to the ultra porousbronze particles 524 in the bonding material layer 522 on the surface ofa substrate 520. The applied lubricative particles 527 infuse the voidedcenters 525 of the ultra porous bronze particles to enhance thelubrication associated with the particles and reduce the friction on theparticles. The lubricative particles 527 may contain PTFE, graphite orany suitable non-abrasive and/or non-stick material. It should beappreciated that the porous particles may be any suitable porous metalparticles such as stainless steel particles, nickel particles, bronzeparticles, iron particles, titanium particles and suitable particlesincluding a metal and/or metal alloys and also porous ceramic particleswhich can be infused with conductive particles such as carbon.

Additional Material Layers

In a further embodiment, catalyzed bonding materials such as epoxies andurethanes are used in the present method to enhance the bond strengthand lower the curing temperature of the coatings. These bonding agentswill be tailored to the desired end use characteristics and also to thetemperature capabilities of the substrate. In one example, theflexibility of cure temperature and bond strengths is demonstrated bythe bonding of pure bronze particles to a commercial glass-filledplastic engineering component, such as a sliding block contact in anelectrical switch gear. The lightweight, rigid engineering glassreinforced plastic conducts no electricity. By adding a layer of bronze,copper, and silver in successive layers, an impact-resistant material iscreated which contacts a switch gear and makes electrical contact. Thismay be used, for example, for a safety switch, where the safety switchmust be very light weight to respond mechanically quickly in a safetysituation. This embodiment may also be employed in a radio wave andelectromagnetic environment to absorb radio frequencies (RF) andelectromagnetic waves.

In another embodiment, acid or chemical resistance is increased byapplying a protective, non-metallic, non-plastic material such as dryceramic, glass, mica flakes and/or mica particles to the wet bondingmaterial layer. The dry ceramic or mica flakes and/or particles create abarrier or a substantial barrier to an acid or other chemical. Thenon-metallic, non-plastic material may be any suitable materials such asceramics, glass, modified mica, mica, boron nitride, silica nitride andaluminum oxide. The barrier diverts the acid or chemical by creating atorturous path or a maze-like path which the acid or chemical cannotavoid as it attempts to penetrate the protective coating. Therefore, theacid or chemical is prevented from directly attacking a base materialsuch as a metal, by decreasing the inherent permeability and porosity ofa base coating or coatings such as a fluoropolymer based acid resistantcoating.

Referring to FIGS. 6A, 6B and 6C a further embodiment of the presentinvention is illustrated where a coated substrate 600 includes one ormore additional wet bonding material layers applied to the primary orfirst wet bonding material layer based on specific design specificationor manufacturer requirements. The bonding material layers are applied tothe first bonding material layer prior to applying the layer ofsubstantially uniform dry particles. In one embodiment, the additionalor subsequent bonding material layers include different bondingmaterials. In another embodiment, the layers include the same bondingmaterial, which is applied to the first bonding material layer to adesired thickness, such as a thickness, t. First, a desired substrate602 such as a metal substrate is first determined by the manufacturer.Then, the first bonding material layer 604 is applied to the surface ofthe substrate 602. A second or additional bonding material layer 605 isapplied to the first bonding material layer 604. The layer ofsubstantially uniform dry particles 606, which are substantially uniformin shape and size, is applied onto the second bonding material layer ortop bonding material layer. The thickness of the subsequent bondingmaterial layers applied to the substrate are generally predeterminedaccording to a design specification or manufacturer requirements. Asuitable topcoat or final coating layer 608 is applied to the uniformparticles to achieve the final coated substrate. It should beappreciated that the thickness of the bonding material layers orcoatings on the substrate or the thickness of the overall substrate mayvary according to the design specifications. Thus, the final coatedproduct or substrate 600 may be any suitable thickness or composition.Additionally, it should be appreciated that other suitable materiallayers may be applied to the wet bonding material layer based onspecific design specifications or requirements. The material layers mayinclude the same or different materials.

In FIGS. 6B and 6C, the dry particles 606 are uniformly distributed onthe material bonding layer or primer layer 604 so that the dry particles606 are dense and cover every facet of the surface on the primer layer.By using a single layer of substantially uniform dry particles, thetopcoat adheres to the maximum surface area of the particles and therebydevelops an extremely strong bond between the coating layer and theparticles 606 of the underlayment 603 a. In one embodiment, a single,substantially uniform dry particle layer 606 is applied to a substrateto promote the adhesion of a coating to the substrate or product. Inanother embodiment, the method of coating a substrate using theunderlayment as described above, may be repeated to apply multiplereinforcing coatings or reinforcing material layers such as multipletopcoatings to the substrate. In this embodiment, the reinforcingmaterial layers are applied until a desired thickness is achieved. Thedesired thickness may be any desired thickness or suitable thicknesspredetermined by the manufacturer. Thus, the present embodiment of theunderlayment may be used to apply multiple reinforcing coatings orreinforcing material layers to a single substrate and to multiplesurfaces on a substrate.

Referring to FIG. 9, in another embodiment, a wet bonding material layer904 a including relatively small particles 906 b of a suitable lowfriction or soft material such as PTFE or UHMW is first applied to thesurface of a substrate 902 as shown in the left section. Next, a layerof uniform hard dry particles 906 a such as bronze particles or othersuitable hard particles is applied to the wet bonding material layer.Then another layer of the initial wet bonding material mixture 904 bincluding the relatively smaller particles is applied to the dryparticle layer as shown in the middle section. The layers are dried anddissolved using a suitable curing process or other suitable dryingprocess. This causes the top layer or second wet bonding material layerincluding the small soft particles to shrink and distribute the smallsoft particles amongst the hard bronze particles as shown in the rightsection. This creates an abrasion resistant and low friction surface.

Referring to FIGS. 10A and 10B, in another embodiment, an initial wetbonding material layer 1003 including relatively small silver platedcopper flakes 1007 and spherical copper particles 1004 are applied to asurface of a substrate 1002. Then, a second wet bonding material layer1006 including the same mixture of smaller silver-plated copperparticles is applied to the surface. A solvent layer 1008 is thenapplied as a topcoat or final coating on the two wet layers. The layersare then dried using a suitable drying or curing process. This dissolvesthe solvent layer as shown in FIG. 10B, and partially dissolves thesecond or top wet material bonding layer to smoothen and sink the silverplated copper flakes and copper particles in the initial wet bondingmaterial layer. The resultant surface includes hard metal particleswhich resist abrasion while the softer small particles reduce frictionon the surface.

Multiple Underlayments

Referring now to FIGS. 7A and 7B, multiple underlayments, such asunderlayments 703 a, 703 b and 703 c, are applied to a surface of asubstrate. The underlayments are applied to create a thicker film on thesubstrate based on desired design specifications or other suitabledesign requirements of a manufacturer. Two or more underlayments 703 maybe applied to the surface of the substrate. In FIGS. 7A and 7B, in oneexample, a substrate 702 is first coated with a first layer of a wetbonding material 704 a. A first substantially uniform layer of dryparticles 706 a is applied to the first bonding material layer 704 a. Asecond bonding material layer 704 b is then applied to the first layerof dry particles 706 a. Then, a second substantially uniform layer ofdry particles is applied to the second bonding layer 704 b. A thirdbonding material layer 704c is applied to the second uniform layer ofdry particles 706 b. A third layer of substantially uniform dryparticles 706 c is applied to the third bonding material layer 704c. Thecombination and thickness of the layers or film is determined by thedesired design specifications for the layers on the surface of thesubstrate. A suitable topcoat or final coating material 708 is thenapplied to the final uniform particle layer 706 c. It should beappreciated that any suitable thicknesses or coating layer or layercombinations may be applied to the surface of a substrate.

Referring to FIGS. 7C and 7D, another example of the embodimentillustrated in FIGS. 7A and 7B are illustrated where the multipleunderlayments include substantially spherical particles 706 a, 706 b and706 c. In FIGS. 7E and 7F, the particles 706 a, 706 b and 706 c areangular particles which are applied in the underlayment layers. Itshould be appreciated that any suitably shaped uniform particles may beapplied to the wet bonding material layers based on the designspecifications and end-use criteria.

In the alternative embodiments of the present invention, if wearresistance is required, then the second layer or layer of substantiallyuniform dry particles is generally the final layer applied to thesurface of a substrate. If non-stick or high corrosion resistance isrequired, then a third and/or fourth wet coating layer or topcoatincluding a suitable non-stick material or similar material is added tothe above layers to increase the non-stick characteristic of the surfaceof the finished, coated substrate.

Several different types of additives may be added to the topcoat orfinal coating to improve the performance characteristics of the coatedsubstrate. In one embodiment, a counterface or opposing surfacesmoothening additive including relatively hard, relatively smallerparticles, is added to a topcoat or final coat, to enable the coatedsubstrate to smoothen or polish a rough surface or surfaces, whichcontact the surface of the coated substrate. In one example, when roughmetal surfaces rub against PTFE coated substrates, the PTFE wears away.Quickly, this diminishes the quality and performance of the PTFE on thecoated substrate. To remedy this problem, a smoothening additive isadded into the wet topcoat of PTFE so that the topcoat or outer layer onthe surface of the substrate contains harder particles than the countersurface such as a metal surface. The relative motion between the surfaceof the coated substrate and the rough metal surface (i.e., theinterface), causes the additive particles to disperse as the particleswear away, and also polishes or smoothens the opposing surface ofrelatively rough metal so that the PTFE topcoat is not worn awayprematurely. This also enables the layer below the topcoat to have asmooth counter surface to work against. It should be appreciated thatany suitable additive may be added to the topcoat or final coating toimprove the performance or desired characteristics of the coatedsubstrate.

Examples

The above embodiments may be employed in several types of coatingprocesses. In one example, a soft coating, which is commonly used tocoat surfaces of cooking equipment, is applied to one or more surfacesof a substrate.

The surface is prepared with cleaning and/or grit blasting to uniformlyroughen and clean the oxide layer off the surface, whether it bealuminum, aluminum oxide, steel, glass, ceramic, plastic or any suitablematerial. A primer bonding mixture or solution including a wet layer ofa polyamide-imide (PAI) material is solvated in or dissolved in asolvent comprising a resin such as N-methylpryrrolidine (NMP) is sprayedonto the surface of the substrate so that the thickness of the wetmixture or solution is approximately between 30-50 microns thick.Alternatively, other suitable application methods such as dipping thesubstrate into the solution or flowing the mixture or solution onto thesurface of the substrate may be used to apply the solution to thesurface of the substrate. The solids in the PAI is approximately fifteenpercent and solids in the NMP vehicle is approximately eighty-fivepercent. Dry particles or granules of aluminum oxide are then applied tothe bonding layer. Preferably, the aluminum oxide particles protrudethrough and are held by the bonding layer. The particles in this exampleare approximately 50-60 microns in size which, when the bonding layershrinks because it is comprised of eighty-five percent solvent andfifteen percent PAI resin, leaves a rough surface not unlike commercialsandpaper. The exception is that each particle has been completelycoated with the diluted primer bonding mixture.

In this example, the dry particles are completely coated with the primerbonding mixture because the dry particles are one hundred percentsolids, where the primer bonding mixture is primarily a liquid includingapproximately twelve to twenty-five percent solids. As the liquidbonding material shrinks, it adheres the particles to the substratethrough adhesive bonding of the amide-imide to the substrate to itselfand to the introduced particles. The resultant underlayment is cured atapproximately 300-600 degrees Fahrenheit, depending on the subsequentcoating or coatings, if any, which may be applied to the underlayment.

In another example, an amide-imide (AI)/PTFE primer or intermediatecompatible material layer, which is compatible with and bonds to theamide-imide layer is applied to the substrate. In this example, thematerial layers are not cured. However, in one embodiment, a semi-cureof 400 degrees Fahrenheit is used after this phase to cure the layers onthe substrate. A relatively pure PTFE coating dispersed in water andsome added component of NMP is applied on top of the intermediatePTFE-AI layer. This last coat is flash dried at approximately 200degrees Fahrenheit until all the water is removed. What remains is thealuminum oxide material held to the surface by, at the bottom of theparticles near the substrate, a pure layer of PAI. The next layer stillcovering the dry aluminum oxide particles includes the intermediate orprimer layer of the PTFE topcoat. In one embodiment, the PTFE topcoathas a thickness of approximately 10-15 microns. The intermediatePTFE-PAI coating is in a dry state and has a thickness of approximately10-20 microns. The purpose of this method is to cover the largestparticles of aluminum oxide to approximately 10-15 microns with aPTFE-rich topcoat. The resulting system is passed through an oven withtemperature zones of approximately 400 degrees in a first phase toapproximately 600 degrees to approximately 800 degrees in a third phase.At approximately 400 degrees, the remaining NMP in the basecoat comesthrough the liquid layers and helps to unify the bond of all threeoriginal liquid layers all of which contain amide-imide (Al). Atapproximately 600 degrees Fahrenheit, all of the volatiles and solventsare removed by heat evaporation, along with any wetting agents. Atapproximately 800 degrees Fahrenheit, the PTFE sinters to itself, theamide-imide bonds to the substrate and to the PTFE with a very high bondstrength, and the dry aluminum oxide particles are held together by boththe lower layer and the intermediate layer of electrostatic AI coating.

In the above example, wear of the PTFE, which is soft and has non-stickproperties, is substantially minimized on the surface of the substrate.Over time, the PTFE layer is worn away until the wear-producing objector objects contact the aluminum oxide layer, which has a substantialhardness of nine on a Mohs' scale. This near-diamond hard materialincludes jagged peaks as its particulate shape is very angular andmulti-faceted. As the entire system is worn, only the peaks of the dryaluminum oxide layer stick through and support each other during thebonding of the lower and intermediate layers. The strength and hardnessof the aluminum oxide layer prevents the PTFE from being worn awayeasily as the rough “mountains” or peaks of aluminum oxide havesurrounding “valleys” filled with PTFE, which is protected by thealuminum oxide “mountains.” In fact, the aluminum oxide layer must beworn away before the PTFE is able to be worn away. The chemical andmechanical bonds of the PTFE layer to the intermediate and lower layersare so strong that the layers are not dislodged even from substantialcavitation pressures or hydraulic pressures. Essentially, the entireunderlayment is locked or secured together. In one embodiment, thequantity of PTFE at the surface is reduced as wear takes place. However,even the partially worn underlayment remains effective as a non-sticklayer such as a food contact release when the underlayment stillincludes approximately 50% PTFE. The PTFE remains effective because thelow surface energy of the remaining PTFE layer repels any sticky orsubstantially sticky products. It should be appreciated that othersuitable ceramic or metallic materials including non-stick or lowersurface energy characteristics may be employed in the above embodimentinstead of aluminum oxide.

In another embodiment, the shape of the dry particles or granules ischanged such as to a rounder or spherical particle in a wear resistantapplication so as to minimize wear or “scratching” of an opposingsurface. Additionally, using softer or harder ceramic materials orparticles reduces the wear or scratching of the opposing surface orsurfaces. As a result, the underlayment can be used in several differentapplications or products such as on the bottom of a frying pan, whichhas little or no PTFE.

In a further embodiment, higher temperature, rigid imide resins ofparticle sizes similar to those of aluminum oxide, approximately 40-60microns, are used to make an even tougher system including no ceramicmaterial and with a more cushioning or softer effect on the opposingcounterface or surface. In one example, a conveyor for transportingglass could be processed using the non-ceramic underlayment particlesand provide extraordinary wear yet very slippery surfaces that will notscratch the glass surfaces transported on the conveyor.

In a further example, the amide-imide is used as a bonding material orprimer in the underlayment. Also, round bronze dry particles that can besolid or porous, are used in the underlayment instead of abrasive,angular particles. As a result, the underlayment provides wearresistance and reduction in an oil-wetted or oil-containing environment,such as in an automobile shock absorber. Additionally, other automobileparts including wear surfaces such as the rod guide and the wear band ona piston, can be manufactured using the underlayment of this embodiment.Furthermore, graphite, molybdenum disulfide or other additives can beadded to the intermediate layer and/or upper coating or topcoat layer toimprove the lubrication characteristics of the automobile or applianceparts or other similar parts or products. In the above embodiments, thedry bronze particles are covered by a PTFE or PTFE/resin materialincluding wear-reducing agents such as molybdenum disulfide, graphite,talc, or particles of lead, zinc, antimony, tin, titanium or any othersuitable material. Thus, the above embodiments may be used forcommercial sliding tables, machine tools, automobile parts and othersimilar applications to enhance the wear resistance and load carryingcapacity and still minimize the friction on the PTFE or PTFE containingintermediate and topcoat layers.

Different Sized Particles

Referring back to FIG. 3 in another embodiment, two different sizedparticles are applied to a substrate 302 to further enhance thewear-reducing capabilities of a surface of the substrate. The bondingmaterial layer or primer layer 304 is applied first to the surface ofthe substrate 302, and then several large, dry metal particles 306 asuch as 125-micron bronze particles are applied to the bonding materiallayer. Then smaller metal particles 306 b such as 25-30 micron leadparticles are applied to the initial metal particle layer as anintermediate coating layer or as a topcoat layer. The underlayment ofthis embodiment therefore provides different wear characteristics basedon the different counter surfaces and surfaces of a substrate orsubstrates.

Referring now to FIG. 8, another embodiment of the present invention isillustrated where the underlayment includes a single uniform layer ofsubstantially spherical or round, dry particles 806. The sphericalparticles are substantially uniform in size and shape and are applied toa bonding material layer 804 on a surface. A suitable topcoat or finalcoating 808 is then applied to the uniform particles. The uniform sizeand shape of the spherical particles promotes the increase of thesurface area for a coating to bond to the particles and also reduces therelatively soft particle coating wear rates. It should be appreciatedthat any substantially uniform size or shaped particles may be employedin the present invention to form the underlayment.

Coating Application Methods

In further embodiments, the coatings are applied using differentapplication methods, which change the structure or bonding strength ofthe underlayment. In one embodiment, one or more suitable solvents orsolvent-catalyst blends are sprayed or applied to the bonding materiallayer on the substrate simultaneously with the substantially uniformparticles. The resultant spray or application method appears as a typeof atomized spray, which enables the process to more completely wet thesurface of the substrate. This process creates an even stronger bondbetween the bonding material layer and the uniform particles.

In another embodiment, a powder spray process is used, which enables anoperator to better control the application of the layers to thesubstrate. The powder spray process applies the uniform particles asvery fine particles to the lower layers adhered to the surface of thesubstrate. This process enables an operator to control the density ofeach of the layers applied to the substrate and also enables theoperator to coat odd-shaped substrates with more control and accuracy.In a further embodiment, the electrostatic powder spray is used to applya topcoat such as a powder paint coating or fluoropolymer powder coatingto the surface of the substrate. In this embodiment, a bonding materialand then a conductive material or coating is applied to the surface ofthe substrate. The powder coating is then cured in a convection orinfrared oven, and because the powder coating does not include solvent,the heat from the oven heats and shrinks the powder coating onto the topof the dry particles. This type of topcoat may be used in many differentindustrial applications such as to produce electrical characteristics orincreasing abrasion resistance of commercial bakeware and cookware.

In a further embodiment, electrostatic, tribo-charged or oppositeelectrostatic charged powder technology is used to further enhance thedry particle attachment or adherence to an odd-shaped configuration. Thedry particles may be electrically insulative, but treated with a veneerof very thin conductive or insulative materials, such as the materialssold by the Ransburg Corporation, for creating electrostatic propertieson substrates such as wood. In one embodiment, the dry particles are“soaked” with these electrostatic enhancing coatings or materials andsubsequently dried or applied in a wet state with more conventionalspray gun technology designed for wet materials. If the harder particlesare ceramic and the configuration is very odd and angular, such as a fanhousing or fan blades, electrostatic powder technology enhances thedistribution of the dry particles. The bonding material layer or primeris altered to provide maximum electrical grounding potential by usingsolvents that are electrically conductive and contain water in somecases. This provides the maximum attraction of the dry particles to thebonding material layer, which provides a uniform, dense coating asdesired by the application in all areas of a vessel or industrialcomponent, such as a fan blade as shown in a centrifugal fan or turbine.

In the tribo-charging process, the tribo-charging is accomplished bystripping the electron off a particle of powder. This is accomplished bypassing the particle over an opposite charged material that strips theelectron off which is passed to ground or earth. This is commonly usedby passing nylon particles through PTFE tubes by using air pressure tomove the nylon particles at high surface speed over the PTFE surface.The opposite holds true. If PTFE particles are passed over nylonsurfaces, they lose the outer layer of electron charge and are attractedto ground or a grounded article or surface.

In another embodiment, the wet materials can be introduced withconventional spray or electrostatic spray technology to apply thebonding material layer or primer to a surface of a substrate. In oneexample, a shaft, on which a wet bonding material layer is applied, isrolled over an electrostatic, aerated, fluidized bed of approximately100,000 volts passing through an electrostatic grid with the dryparticles suspended over a porous membrane of polyethylene. When airpressure is introduced underneath the electrostatic grid in an open topcontainer, the dry particles become charged by the air passing throughand past an electrical grid, which is placed slightly below theinsulated polyethylene membrane. The charged dry particles above theporous polyethylene membrane are uniformly attracted to the wetsubstrate on the surface of the shaft, which is suspended and rotatedabove the fluidized bed. Because of the self-limiting characteristics ofthe electrostatic method, the dry particles are uniformly applied as theparticles are applied to the substrate. The applied dry particles, asthe particles are deposited, create an insulated layer in the areaswhere the dry particles are attached or attracted to the wet bondingmaterial layer. This method provides a very uniform application of thedry particles to the surface of the substrate at high speeds and at lowcommercial costs.

In a further embodiment, the substantially uniform aluminum oxideparticles are applied to a surface of a substrate to achieve a desiredroughness on the surface. The desired surface roughness is achieved bychanging the size of the aluminum oxide particles applied to thesurface. The aluminum oxide particles are applied to a thin bondingmaterial layer on a surface of a substrate and create a very strong bondwith the surface of the substrate. The aluminum oxide particles may beapplied to various surfaces including the surfaces of rigid parts. Theapplication of the aluminum oxide particles to roughen the surface orsurfaces of a substrate substantially minimizes the distortion to thesurface, which occurs with conventional blasting methods, and enables auser to control the roughness of the surface. In addition, harderparticles such as boron nitride particles or other suitable particlescan be applied to the surface of the substrate to increase thepenetration resistance of the surface.

Selective Application of the Uniform Particles

The wet bonding material layers are generally applied to the entiresurface of a substrate. In one embodiment, the uniform particles areapplied onto the entire wet bonding material layer. In anotherembodiment, the uniform particles are applied to specific areas on thewet bonding material layer on the surface of the substrate. In thisembodiment, a mask of a suitable masking material is applied to the wetbonding material layer to prevent the adherence of the uniform particlesto the masked areas. Thus, a surface of a substrate such as a particularsurface or portion of a surface of a part can be masked or selectivelycoated with a suitable masking material so that the dry uniformparticles are applied to specific areas of the surface of the substrate.In one example, specific surfaces of a cooking pan such as a saute panor wok are selectively coated with a non-abrasive and/or non-stickmaterial to reduce abrasion and wear on those surfaces of the pan. Ametal utensil is commonly used to stir or mix food products in the pan,which causes abrasion of the surfaces of the pan. The abrasion isgenerally focused on the bottom surface of the pan and not the sidesurfaces because the bottom surface of the pan gets hot causing the foodproducts to stick to the bottom surface. Efforts of a user to dislodgethe food product from the bottom surface using a metal or similarutensil, concentrates the vast majority of the wear on the bottomsurface of the pan. Therefore, to increase the abrasion resistance ofthe bottom surface of the pan, a wet bonding material layer is appliedto the entire cooking surface of the pan followed by a selectiveapplication of abrasion resistant particles, such as relatively hardparticles, to the bottom surface of the pan. This is accomplished byapplying the wet bonding material to all of the surfaces of the pan.Then, a mask or suitable masking material, which does not allow theuniform particles to adhere to or partially adhere to it, is applied tothe surfaces of the pan except the bottom surface of the pan. Theabrasion resistant particles therefore, will only adhere to the bottomsurface of the pan and not to the masked surfaces. In one embodiment,the above applications are followed with a thin application layer ofsmaller sized dry reinforcing particles to the entire surface of thepan. In all cases, a topcoat including a non-stick material is appliedto the entire surface of the pan.

The present embodiment can also be used in industrial applications toreduce cost and/or improve machine tolerances. In one example, thecylindrical area and top of the valve are coated with the wet bondinglayer. A uniform dry particle layer is applied by then inverting thesolenoid valve so that the uniform dry particles contact the sides ofthe cylindrical area of the solenoid while it is being rotated. Gravitycauses the excess dry particles to drop down providing no dry particlesthat are adhered to the bottom wet area of the valve of the solenoid.The solenoid surfaces are then completely cured using a suitable curingprocess. Subsequently, bronze particles are applied to the outsidesurface of the cylindrical area and then covered with a thin,appropriate topcoat. The face of end surface of the solenoid is onlycoated with a single coating of the original wet bonding material layer,which has been cured as described above.

Magnetic Particle Embodiment

In a further embodiment, dry magnetic particles are applied to the wetsurface of a glass or non-magnetic metal substrate to completely coatthe surface of the substrate. In one aspect of this embodiment, amagnetic shape is placed on a surface to be coated, either under, aboveor both under and above, the surface. The magnetic shape may be anyshape, symbol, character or other suitable image. The shape will appearon the surface of the substrate as the magnetic particles orientthemselves due to the magnetic forces attracting the magnetic particleswhile the magnetic particles “float” in the liquid layer. A suitablenon-magnetic material, such as aluminum or glass, is used as thesubstrate.

One example is a glass or metallic baking pan. A wet bonding material isfirst applied to the surface. Magnetic particles, such as magneticstainless steel or magnetic iron particles that are dry, are applied tothe non-magnetic pan. The wet bonding layer stays moist during this drymagnetic particle application phase. A magnetic image, which might be acompany logo, part number, identification or other suitable identifier,is created with a highly magnetic force field. This may beelectromagnetic or magnetic in nature comprising a predetermined shape.The magnetic shape can be suspended below and in contact with the pan orit can be suspended slightly above the surface of the magneticparticles, not touching the particles. The magnetic forces will affectthe magnetic material that has been introduced as a dry particle to thewet base bonding layer and the shape of the magnetic forces will beshown in the pattern in the coating created by the orientation of themetallic particles.

Various blends of metallic particles can be used and various shapes canbe blended into the dry layer so that very distinct images appear in thelayer depending on the formulations of the dry particles. In oneexample, a coffee cup that has had a wet bonding layer applied followedwith an application of the dry magnetic material can have a company logocreated with an electromagnet or solid magnets, such as Rare Earth orAlnico magnets, which will orient the magnetic particles that have beenintroduced to the wet bonding layer to create an image that is that ofthe company's logo. It should be appreciated that the letters would bereversed, in mirror images, if placed below the pan so that the viewingof the pan from the topside, where the wet bonding/dry magnetic particlelayer is applied, reads correctly. This could be followed immediately,while the magnetic forces are held in place, with a semi-curing infraredheat cycle which would harden the wet bonding layer so that theorientation of the magnetic particles while they are being magnetizedwould hold the formed shape. In this embodiment the magnetic particlesmay be ferrite particles, ferrous particles, or any suitably magneticmaterials, including stainless steel. In one aspect of this embodiment,the magnetic particles are densely packed at the surface due to theforces the magnetic field places upon the particles at the surface andon the surface of the substrate. The magnetic contraction or alignmentoccurs within the wet bonding layer while the magnetic particles “float”before the wet bonding layer is hardened through a curing operation.

In a further embodiment, ferrite particles are applied to the surface orsurfaces of a substrate over a wet bonding material layer to absorbmicrowaves or similar waves such as in a microwave oven. For instance,the ferrite particles may be applied to a wet bonding material layer ona glass container. This step is repeated several times until the ferriteparticles, which are chosen for their microwave absorptive capabilities,have sufficient depth to create and transfer energy in the form of heatto food products inside the glass dish while in a microwave oven. Inthis embodiment, the entire glass dish or bowl would be coated with thewet bonding material layer, which would be opaque in nature. The ferriteparticles are introduced only to the bottom of the dish. This wouldallow, when the complete system is cured, for the microwave energy to beabsorbed in the center of the dish. For example, a microwave popcornmaker could be made in such a manner in which the heat was concentratedat the bottom of the microwave vessel, container or dish allowing thenewly popped corn to leave the hot surface and be replaced by heavierand denser popcorn as it falls into the center of the curved dish. Inanother example, medical sterilization equipment could be manufacturedwith plastic and the bonded ferrite layer, which would produce localizedheat in certain areas of the plastic as determined by the introductionof the ferrite particles where necessary.

In a further embodiment, the coated substrate is cured using inductionheating. In this embodiment, induction or magnetic sensitive particlessuch as uniform metal particles are applied to the wet bonding materialon the surface of a substrate. The metal particles may include uniformmagnetic stainless steel flakes or stainless steel particles. The flakesor particles are rearranged in the wet bonding material using a magnetor other suitable magnetic device. Induction waves, which are reversemagnetic fields, are then directed at the coated substrate to induceheat in the wet bonding material. The heat induced in the wet bondingmaterial cures the wet bonding material to produce the final coatedsubstrate. In another embodiment, an induction heat device is used toraise the temperature of the substrate and thereby cure the wet bondingmaterial layer.

Density of Uniform Particle Layer

In a further embodiment, the strength of the bonds and the layers on thesubstrate are increased by increasing the density of the uniform dryparticles that are applied to the bonding material layer on the surfaceof a substrate. In one aspect of this embodiment, commercial, unmodifiedor modified grit blasting or sandblasting equipment is employed to applythe dry particles to the bonding material layer. The density of theparticles in the bonding material layer is increased by increasing thepressure of the spray and the velocity of the dry particles and the rateof speed in which the coatings are applied to the bonding materiallayer. The increased pressure of the dry particle depositing spray andthe rate at which the dry coating or dry coatings are applied to thebonding material layer, increases the packing or density of theparticles in the wet bonding material layer. The pressure of the sprayand/or the rate of speed of the spray may be adjusted to maximize thedensity of the dry particles based on the desired design specifications.

The high-speed introduction of particles into the bonding material canalso be used when multiple-sized dry particles are applied to thesurface of a substrate. In one example, a first layer includesrelatively small particles of approximately 20-50 microns, followed bythe application of relatively large particles of approximately 150microns followed by the application of relatively small particles ofapproximately 20-50 microns followed by the application of smallerparticles of approximately 10-20 microns. In this embodiment, thedensity of a 30-40 micron wet bonding material layer is increased andalso the interconnectivity or contact between particles is enhanced.This layer, when wet, will be 30 microns, but the finished layer mayactually be greater with the 150-micron particles protruding from thesurface and causing the surface of the substrate to be slightlytextured.

Particle Encapsulation

In an alternative embodiment, the substantially uniform dry particlesare pre-treated, encapsulated or micronized with a wet bonding materialsuch as an adhesion promoting encapsulent or catalytic reactive materialproducing encapsulent prior to being applied to the wet surface on asubstrate. One example of an adhesion promoting encapsulant is a silanecoupling agent or silane. The wet bonding material applied to the dryparticles may be the same or different from the wet bonding materialapplied to the surface of the substrate as described above. Preferably,the bonding material is compatible with the bonding material layerapplied to the surface of the substrate and any other coating layersapplied to the substrate. In one embodiment, the particles are placed ina rotary device such as a tumbler. The bonding material is sprayed orapplied as droplets into the tumbler and thereby evenly distributes andcoats the dry particles as the particles rotate in the tumbler. Thebonding material basically coats all of the areas of the dry particleswith a thin veneer. The coated particles are dried or semi-cured toencapsulate the dry particles, and then applied to the wet bondingmaterial layer.

In one embodiment, a curing cycle is employed to semi-cure the wetbonding agent or bonding material, which contains a resin and a solventto the once dry particles. The extra curing process enables the dryparticles to adhere to each other and also evaporates or removes thesolvent from the base or initial coating layer, which strengthens thebond between the dry particles and a intermediate or lower layer on asurface of a substrate. Thus, pre-coating or pre-treating the dryparticles with a bonding material enhances the bonding capabilities ofthe particles to each other and enhances the bonding strength betweenthe particles and the bonding material layer on the surface of thesubstrate and subsequent applied layers.

Wave Absorption Embodiment

In one embodiment, the present method is used to attenuate or absorbmagnetic, electromagnetic, radio or other airborne waves or signals suchas in a medical X-ray room or similar area such as in RF shielding.Currently, sheets of metal such as copper or similar materials are usedto cover the surfaces in these areas. In the present method describedabove, a wet bonding material is applied or sprayed onto a vertical orhorizontal surface or substrate such as a wall or floor in a room. Inthis embodiment, it should be appreciated that the base material layersuch as the bonding material layer may have a thickness of approximately125-150 microns.

After the wet bonding material is applied to the surface or surfaces, asuitable magnetic wave or other suitable absorbing type material such asdry copper particles, which may have a thickness of approximately 50-75microns, are applied to the wet bonding material layer. These relativelysmaller particles fill in the areas that are still wet between thelarger particles. Additionally, a leafing material such as silver,nickel, copper, bronze, or any other conductive material may be appliedto the uniform dry particles. Once the coated substrate is groundedusing the leafing material, the entire exposed surface acts as anelectrical conductor such as a sheet of metal. Thus, additional layerscan be added to the multiple layers of the original formulation ofprimer or bonding material. The sequence can be repeated until thethickness of the layers is approximately 400-500 microns or greater. Themultiple sized particles in this underlayment contact each otherinterconnectedly to provide an essentially impermeable barrier to radiowaves or any other airborne electromagnetic or electronic waves.

The benefit of the underlayment including the wave reducing or absorbinglayer is that the metallic particles are densely compacted into the wetbonding material layer. In conventional coating processes, the particlesare applied to the surface of a substrate as a part of the wet coatingand therefore, the coating may actually prevent contact between theparticles. Conversely, careful formulation of the bonding material layeractually produces a shrinking or cohesive effect which increases thedensity of the layers as the layers are dried or catalyzed in place.

Thus, the present invention enables the dry copper particles tocompletely cover the desired surfaces and thereby minimize or eliminatethe gaps and seams produced by conventional methods, which cover or linewalls in a room with sheet of metal such as copper. Additionally in oneembodiment, a flexible bonding material is used to enable the coatingsto better adhere to the surfaces, twists and bends of the surfaces suchas corners in a room. In one aspect of this embodiment, to enhance theadherence and coverage of the particles to the bonding material layer,an electrically conductive bonding material is used to attract theoppositely charged particles.

In RF shielding on plastic, many materials have been used which containleafing particles of copper, bronze, and other similar materials toprovide a metallic shield over plastic parts. In all cases, these liquidcoatings with high-solids metals had problems with distribution of theparticles because of the settling characteristics of the heavy metals,particularly the copper and bronze. Also, the uneven distribution ofparticles caused the particles to remain substantially separated by thecarrier resin, which negatively affects the conductivity of the coating.Thus, the coatings must be applied thicker and thicker to minimize oreliminate the voids or separation of the particles in the coating whereradio waves or electromagnetic waves may permeate an opening in thecoating or coatings.

Adhesives

In one embodiment of the underlayment of the present invention, thematerials can be more effectively bonded to the plastics using two-partadhesives, such as epoxy and urethane and a very dense metallic layer,which would include pure metal interconnecting metallurgically withintimate particle-to-particle contact. In this embodiment, theimpingement velocity of the dry particles sprayed onto the wet bondingmaterial causes the dry particles to stick to the bonding materiallayer, which provides a dense particle layer. The density of theparticle layer may be increased by using multi-sized and multi-shapedparticles. The dry particle layer can be electrically tested beforefurther coatings are applied to the dry particle layer. This enables auser to be able to test the conductivity of the coatings beforeadditional layers are applied and also enables the user to reinforce asection or area of the underlayment with more particles, if moreparticles are needed based on the conductivity.

INDUSTRIAL APPLICATIONS

In another embodiment, industrial sifters, strainers, filters andsimilar industrial components, which are comprised of thick plates withperforated holes, are completely coated with wear resistant coatingusing the underlayment of the present invention. For example, commerciallaundry dryers used in hospitals can be six feet or greater in diameterand ten feet or longer, comprising of several curved plates bolted to astructure, which resembles a drum when complete. In this case, thescraping of clothing and plastic items against the non-stick surface orsurfaces of the dryers wears the surfaces away. Using the underlaymentof the present invention, the non-stick surfaces of the dryers issubstantially strengthened and the wear resistance of these surfaces issignificantly enhanced.

In another example, a surface or surfaces of industrial centrifuges arecoated. Industrial centrifuges incur great wear during operation. Withconventional technology, hard particles such as stainless steelparticles are made molten and directed towards a surface or surfaces ofa substrate such as by using an arc spray or plasma detonation withdetonation gun technology, to increase the roughness of the surface orsurfaces. This application method, however, typically coats the surfaceor surfaces which are at right angles to or directly impacted by thespray, but fails to completely coat the inside surfaces of verticalholes which are on surfaces parallel to the direction of the spray.

In the embodiment of the present invention, by using electrostatic spraytechnology to apply the bonding material layer to the surface orsurfaces of the substrate, the uniform dry particles completely coverthe flat surface of the inside of the centrifuge, but also, all of theholes that allow media to pass through the centrifuge. By using thiselectrostatic combination of liquid and subsequent powder-sprayapplication, the inside surface which defines the holes are strengthenedthrough the uniform application of the wear resistant dry particles.Present technology does not strengthen the inside surfaces of the holes.Thus, in conventional centrifuges, the media passing through the holeseventually wears away the soft non-stick coating on the surface orsurfaces of the surfaces of the centrifuges. With the present invention,the flat surface and the surface which defines the holes are completelycoated and protected. This is substantially different than theconventional technology in that the distribution of the wear-resistantparticles in the conventional technology is focused on the flat surfacesand does not completely coat the surfaces. With the present method, theelectrostatic attraction of the particles to the wetted surfaces,ensures complete coverage of the bonding material layer to the flatsurfaces and the holes.

In a further embodiment, the present invention is employed in a rotarymolding system such as a reactor or commercial dryer vessel to improvethe wear resistance of the system. The predetermined quantity of bondingmaterial is filled into the vessel such as the reactor cavity or maindryer compartment and rotated in a multi-directional manner tocompletely and uniformly coat the inside surface of the vessel. Then,suitable substantially uniform abrasive-resistant particles or othersuitable particles are filled into the vessel and are applied to thebonding material layer on the inside surface of the vessel using themulti-directional rotation of the vessel described above. After the dryparticles coat the surface, the vessel is inverted and the excessparticles drop out of the vessel. The bonding material and dry particleson the surface are cured using a suitable curing process and a finalcoating or topcoat is then applied to the uniform particle layer ifdesired.

In one example, a powder fluoropolymer topcoat, such as PFA or FEPincludes a combination of either a resin with PTFE and/or any suitableand appropriate modifiers and strengthening agents, such as graphite,talc, and lead powder. The underlayment is created and cured at atemperature of approximately 750 degrees Fahrenheit or lower, dependingon the bonding resin or material that is used in the process. Thefluoropolymer-rich topcoat, which is in powder form, is applied to theunderlayment for wear resistance, if necessary, such as in a machinechannel or guide or commercial baking pan or similar bakery or foodprocessing equipment.

The underlayment, if it consists of aluminum oxide or similarabrasion-resistant particles, which are very hard, is coated With thefluoropolymer powder mixture and FDA or food contact ingredients areselected to comply with FDA requirements. This allows the creation of ahighly wear resistant, non-stick coating with a powder topcoat.

In another example, preparation for arc spraying stainless steel wireand titanium wire, to create a bumpy or rough base requires an extensiveamount of grit blasting and surface preparation to roughen the surfacefor the mechanical grip such that these dissimilar metals, when impingedin a molten state on the surface, cannot bond metallurgically. With theunderlayment of the present invention, the dry uniform particles arebonded and tightly adhered to a surface of a substrate throughcontemporary adhesive technology and function at and beyond thetemperature constraints of typical topcoatings, such as PTFE, which hasa limit of approximately 550 degrees Fahrenheit. In other words, theadhesive bond strength and temperature capacity of the underlayment isgreater than the temperature capacity of the subsequently appliedtopcoat layers or topcoats.

Multiple Coating Applicators

In an alternative embodiment, a coating system includes a plurality ofcoating or material applicators, at least one container having a wetbonding material, at least one container having substantially dryparticles, wherein the containers are connected to the coatingapplicators using at least one coating line or tube, which transportsthe materials from the containers to the coating applicators. It shouldbe appreciated that the coating applicators may be spray guns,electrostatic spray guns, powder spray guns or any other suitableapplicators. The coating applicators are positioned adjacent to thesurface or surfaces being coated on the substrate.

In one aspect of this embodiment, one of the coating applicators appliesthe wet bonding material to the surface of the substrate and the othercoating applicator applies an even, substantially uniform layer of thedry particles to the wet bonding material layer. The applicators mayapply the coatings at the same rate or at different rates. The coatingapplicators apply each layer to the surface of the substrate until adesired thickness is achieved.

In one example, the coating system includes multiple coating or materialapplicators such as two electrostatic spray guns or powder spray guns,to apply an epoxy-based material to a surface of a substrate. The epoxyis made up of relatively dry particles which are applied usingelectrostatic attraction to the surface. While the dry epoxy is inplace, a thin layer of a wet bonding material is fog-sprayed or appliedto the dry epoxy particles to slightly dampen the surface of theparticles. Then, a powder spray of aluminum oxide, bronze, ceramic,glass or any other suitable material is applied to the bonding materialon the particles. The layers are then heated or cured. Subsequently, afinal coating such as a wet or dry film, may be applied to the curedlayers. In one example, an epoxy base is applied to the surface of thesubstrate. Then, a wet film including a solvent and water is applied tothe epoxy to wet the epoxy and provide some stickiness on the surface. Adry powder spray of non-electrostatic particles are then applied to thesurface.

It should be appreciated that the underlayment of the present inventioncan be used as a single process without any topcoats to provide adhesionof paper or grip or tractive strength as related to moving paper orother products with a roller at high speeds. Additionally, theunderlayment could be created with approximately 30 to 40 micron thickbonding material layer and an approximately 200-micron sharp particlesof aluminum oxide or boron nitride or other very high-wear resistantceramics and provide an abrasive gripping surface.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present invention andwithout diminishing its intended advantages. It is therefore intendedthat such changes and modifications be covered by the appended claims.

1. A method of forming a non-stick coating on a surface of a substrate,said method comprising: (a) applying an electrically orelectrostatically grounded non-stick wet bonding material to the surfaceof the substrate; (b) coating the bonding material with a layer ofsubstantially uniform copper particles, wherein the copper particleshave an electrical or electrostatic charge opposite the electricalcharge of the bonding material; and (c) at least partially curing thewet bonding material and the substantially uniform copper particles,such that a plurality of the copper particles are substantiallysubmerged Within the cured bonding material and at least part of saidcopper particles protrude from the cured bonding material.
 2. The methodof claim 1, which includes applying a topcoating to the bonding materialand the copper particles.